Understanding Obtaining FE+ Troops In Ages before Contemporary Era

This might be a bit of a long post, because there's a lot involved with how this works and rather than saying "just do this" I'm going to try and explain everything that's going on.

If a "just do this" post *is* what you want, look here: https://forum.us.forgeofempires.com/index.php?threads/higher-age-units-guide-v1-22.37109/

Ok so the process of getting these troops in Contemporary Era+ I've explained before and is relatively straightforward.  Save what you can for techs, and only progress the continent map and research tree when the story tells you you have to.  The reason you can't do this normally in PME or earlier is because of "hard tech blocks" that once they come up you cannot pass without progressing to the age in question.  At the end of each of the CE and PME continent maps there is one of these blocks.

So how do you get by these quests?  You have to stop them from appearing at all.  Starting in Contemporary Era the story occasionally "breaks" depending on your actions.  Story quests have prerequisites and if you've done something unexpected like fighting ahead on the map past where the next quest would be, it skips that quest - if later quests have that quest as a prerequisite, the story can disappear entirely.  This can be useful to get 3 recurring quests in an age that's not the last - but in this case it's going to be used to skip a "hard tech block".  By completing the last province of the CE continent and moving onto the next map while skipping the optional provinces not required before you advance the quests, it'll skip to Dictator's Death, and then the story will disappear.  Presumably "King of the Desert", the CE blocker quest, requires either you to have completed another CE quest that you skipped or to control the whole map.

So your story's gone, that's all well and good - but how do you get the FE troops then?  At various points, the story is eligible to return without you having completed prerequisite quests - just for being at the right spot on the continent map and not having a Story Quest.  We'll call these "resume points".  FE has a few of these.  So we're able to rejoin the story in time to get FE troops.

Now I mentioned that Postmodern Era also has a blocker, "The End of This Chapter".  I also didn't mention the story "breaking" before Contemporary Era.  So...  this one needs to be avoided via an anomaly in the PME story.  At one point near the end of the PME story, they want to give you a choice as to whether to cover up the actions of Colonel Lang or to tell the truth about what happened, "Your Choice: Truth or Dare?".  Apparently in order to make it eligible to abort, they had to flag it as a Side Quest.  This allows "resume points" checking your quests to see that you don't have a Story Quest and as such let you pick up story from that point.  So the core point for getting them before Postmodern Era is to simply never complete or abort "Your Choice: Truth or Dare?".

Ok so that's it for the extra complications in terms of quests...  But there is another detail to deal with - you do have to somehow manage to take all these continents!  To take ME through FE up to hover tanks by negotiation requires ~40k PE+ goods!  That's a lot of goods to purchase, so you might want to fight as much as possible.  

But for large segments of the map you'll be using units 1 or more eras out of date.  Accordingly you need significant amounts of boost.  The attack of units isn't much of a problem in my experience (i.e. if you have the 3 main attack buildings that should cover most of what you need to 2-shot enemy units), but given the awkward armies you're often using the defense of your attacking units is of paramount importance.  So in preparation for attempting this, you may wish to focus on stacking event buildings that offer defense for attacking army.  You will also need a source of a significant number of rogues.

To fight with rogues on continent map you need to move your "real unit" to the corner and keep it far enough away from enemy units that they don't pick it to attack.  Continent map does not prioritize rogues over non-rogues like the AI you're used to from GvG/GBG/Neighborhood battles.  But it does prioritize proximity to a large degree - so parking the real unit in the corner while you fling forward the rogues does often work.  Rapid Deployment units have a tendency to occasionally blast your real unit before you can move it.  And that's a big part of where the need for defense comes in.

Overall summary of process:

BA-LMA: 

• Skip some unnecessary techs - not crucial to reach Hover Tanks or if your target age is Progressive Era but the more you skip the easier it'll be to reach OF troops in Industrial.
• Try to build up rogues and defense bonus for attacking army.  
• Be as caught up as you can be on Story Quests before Colonial Age (you should get stuck on a quest requiring you to build Colonial buildings)

Colonial Age: 

• Carefully enter it researching a minimum of techs.
• Complete Industrial Story and as much of Progressive Story as you can until you get stuck (there's some quests requiring you to build Industrial or Progressive buildings).

Industrial Age+: 

• Continue carefully dealing with tech only as fast as you have to to complete story.  Extreme option is to win Police Stations from events, daily challenges, or expedition so you don't have to use up techs on researching them.
• Finish PE+ME story in whatever manner you prefer.
• Only negotiate with Che Guerrero when required to take one of his provinces in PME, don't take the other yet and don't fight any sectors inside.  This is necessary to receive the MG Teams that you'll be using to fight for the next while.
• Proceed with story as directed along the peninsula where you negotiated for a province from Che.  Fighting or Negotiating is fine with the other leader.
• Receive 5 MG Teams (and some commandos).
• After finishing the one side and being directed by story, conquer Che's other province by whatever means you prefer (you can fight him now if you prefer)
• Finish PME story up to "Your Choice: Truth or Dare?".  Do not complete or abort this quest until you are done trying to get units above your age or are in Postmodern Era.
• Complete the Contemporary Era map without advancing story while not scouting the 2 optional provinces (in the north-west) that are unnecessary to get off the map (in the north-east).  Once you've scouted the first province of the TE map it is safe to advance story (possibly earlier, but if it doesn't work out you may not be able to get Hover Tanks til Contemporary Era) - it should just vanish for the time being.  Complete TE map as you please.
• TE story can be resumed at "Meet Miguel Mantos" immediately after scouting Rio Roxo - and possibly other spots.  Doing so may enable you to win troops useful to fight the rest of TE and FE continent with but may also require more techs.  If you wish to skip the entirety of TE story, you should do the same as CE and take only what you have to and get off the map before advancing story.
• Only negotiate with Joy Danba in the first province in Future Era.
• Upon finishing your negotiations for her entire province, FE story should be ready to resume telling you to scout the next provinces.
• Follow story as directed until you reach the point where you need to scout Kalabuye and Bisoraba (the two provinces adjacent to Botuku).
• Do not touch Kalabuye until Joy Danba has given you 3 Hover Tanks.
• Continue on with story as you please.  You will get 1 more Hover Tank and some assorted other troops.  Tech count permitting, you may continue following story until about halfway through the OF continent map winning a great deal of additional advanced troops.

Guild Battlegrounds through the Ages

We've had Guild Battlegrounds for over a year now - and I've played it in many different ages.  Some of my comments will be theory - but most of them will be extrapolated from experience.  I'm going to try and present it all as a table.  Some setups against some defenses you may need to go into the battle and hold back a non-rogue or two for the first round of combat before pressing auto.

Era	Important Armies	Pros & Cons
Iron Age	4-8 Ballistae + 0-4 Rogues - Good against enemy Ballistae and Archers 1-2 Legionnaires + 6-7 Rogues - Good against enemies without Ballistae 1-2 Mounted Warriors or Soldiers + 6-7 Rogues - Good against enemies with a mix of Ballistae + faster troops	+ Untransformed Rogues kick ass - Reliance on melee units means much damage taken at high attrition unless you work on your defense - Artillery have a hard time keeping up against heavies at higher attrition as much of their strength against them comes from the flat bonus which doesn't scale
Early Middle Ages	4-8 Catapults + 0-4 Rogues - Good against enemy Catapults 1-2 Armored Infantry + 6-7 Rogues - Good against enemies without Catapults 1-2 Heavy Cavalry or Mercenaries + 6-7 Rogues - Good against enemies with a mix of Catapults + faster troops	+ Untransformed Rogues kick ass + Weak-statted Mounted Archers aren't much of a threat to your more durable units - High movement Mounted Archers can occasionally pick off your less durable units - Reliance on melee units means much damage taken at high attrition unless you work on your defense - Artillery have a hard time keeping up against heavies at higher attrition as much of their strength against them comes from the flat bonus which doesn't scale
High Middle Ages	4-8 Trebuchets + 0-4 Rogues - Good against enemy Trebuchets and Crossbows 1-2 Heavy Infantry + 6-7 Rogues - Good against enemies without Trebuchets 1-2 Knights or Berserkers + 6-7 Rogues - Good against enemies with a mix of Trebuchets + faster troops	+ Untransformed Rogues kick ass + Strongest low-age artillery with crazy range and slightly higher relative attack compared to the defense of units of the age - Reliance on melee units means much damage taken at high attrition unless you work on your defense - Artillery have a hard time keeping up against heavies at higher attrition as much of their strength against them comes from the flat bonus which doesn't scale
Late Middle Ages	1-2 Heavy Knights or Great Sword Warriors + 6-7 Rogues - Good against enemies with a mix of Cannons + faster troops 1-2 Imperial Guards + 6-7 Rogues - Good against enemies without many Cannons 4-8 Cannons + 0-4 Rogues - Good against enemy Longbows	+ Untransformed Rogues kick ass + Fast units are starting to get more durable - Combination of Dug In on enemy artillery and less range makes this among the weakest low-age artillery relatively.  They also still have a hard time keeping up against heavies at higher attrition as much of their strength against them comes from the flat bonus which doesn't scale - Reliance on melee units means much damage taken at high attrition unless you work on your defense
Colonial Age	1-2 Grenadiers + 6-7 Rogues - Good against enemies without too many Field Guns or Musketeers 1-2 Dragoons, Champions, or Rangers + 6-7 Rogues - Good against enemies with significant numbers of Field Guns or Musketeers	+ Untransformed Rogues kick ass + Grenadiers gained a range and no longer have to take retaliation - Combination of Dug In on enemy artillery and useful amounts of defense on Musketeers make this among the weakest low-age artillery relatively.  They also still have a hard time keeping up against heavies at higher attrition as much of their strength against them comes from the flat bonus which doesn't scale
Industrial Age	1-2 Howitzers + 6-7 Rogues - Good against enemies without too many Riflemen or Breech Loaders 1-2 Jaeger Infantry + 6-7 Rogues - Good against enemies without too many Howitzers 4-6 Breech Loaders + 2-4 Rogues - Good against enemies with many Howitzers.  May consider adding in a couple Riflemen/Howitzers/Jaeger Infantry if there's a couple things you need to kill off when they get close.	+ Every unit other than the Fast has range - lopsided attack bonuses can be taken advantage of + You can also get many ages of troops ahead here; Up to PME are available from getting ahead on the story.  Note that you either need to be careful or be prepared to spend diamonds to revive them if you're going to use them.  Choices you make on PME map will affect how many/what type of troops you can get.  Make sure to do your research if you're planning to try for them. + Well matched unit abilities make Industrial an age where almost any fight is possible if you choose the right counter.  Fun age to manual battle in. - Many of the units do not behave as well as you might hope in auto-battles making it an age of high losses for auto-battlers
Progressive Era	1-6 Conscripts + 2-7 Rogues - Good against enemies without too many Snipers.  Snipers will get to be slightly less of a problem as you get to higher boost though as they're reliant on a *large* flat bonus. 1-6 Armored Cars + 2-7 Rogues - Good against enemies without too many tanks.  Will need to position your cars for the first round of battle usually. 1-6 Tanks + 2-7 Rogues - Particularly if you stack defense; Tanks have defense naturally higher than any unit in-age's attack so if you have defense boost ~twice as high as your attack boost you may be able to take advantage of that	+ 3 good options for general purpose units depending on what you're fighting and how your stats are built.  If you engineer the fights so that after your last Rogues are turned, they're taking the first "real" hits you're in good shape. - An era of high losses (I want to say attrition, but that has other meaning in game now), there pretty much just isn't *clean* wins.  Two wave battles can also be problematic because of this. - High defense on Tanks may make fights at high attrition impossible unless you've kept up on defense boost yourself so that they're not doing much damage to you either.  MG Team from story + Rogues could patch this issue to some extent if you're careful.
Modern Era	1-6 Bazookas + 2-7 Rogues - Good against armies without too many artillery.  Despite their bonus against artillery and Dug In, they are very very slow - they're best against armies that will come to them, turn the rogues, and then they can blow them up before the problems start.  But they're *really* good against those armies.  Paratroopers can also be an annoyance due to their ability to hide in trees combined with your slow movement. 1-8 Mechanized Infantry/Champions/Battle Tanks + 0-7 Rogues - Good against pretty much anything if you go into battle to position them right for the first turn.  The heavy of the age has the same defense as it did in PE, so they've caught up some in their ability to handle them.  May take heavy losses from ignored Bazookas on auto 4-8 Mechanized Artillery + 0-4 Rogues - Good against Bazookas and enemy artillery.  Dreadful against Paratroopers.  Mediocre against Battle Tanks and Mechanized Infantry. 8 Paratroopers (No Rogues.  Period.) - Move first + hit first is a powerful combination that'll get stressed more in later ages.  It can work here to some extent too.  Main issue is their attack isn't that high - so they might not be able to 2-shot things reliably enough at high attrition - particularly Battle Tanks and Mechanized Infantry.  Still something worth playing with some.	+ Every unit has its moments - even if most people hate to use paratroopers ;) - Can get bloody - not quite as much as PE but still lacks abilities at times to get clean wins and two wave battles may be a problem
Postmodern Era	1-2 MG Teams + 6-7 Rogues - Contact! means every Rogue turned (by anything other than an artillery) also gave you a free shot.  Good against anything without too many artillery. 4-6 Rocket Artillery + 2-4 Rogues - Good at handling enemy artillery 1-6 Universal Tanks, IFVs, or Champions + 2-7 Rogues - can help with some of the problem setups that have too many artillery for your MG teams and not enough artillery to use your own artillery.	+ Contact! + Rogues are a powerful combination + Can get very advanced troops potentially - but the method is somewhat obscure (and I've never tried it yet). - Artillery have low attack making your top choice to deal with Artillery + X struggle a bit with some setups.
Contemporary Era	1-2 Anti-Aircraft Vehicles + 6-7 Rogues - Good against everything.  Only caveat - some defenses you have to go in and hold back your AAV on. 1-3 Assault Tanks + 5-7 Rogues - Taking advantage of Reactive Armor this can be used on some very high attrition fights.  They can't do more than 4 to you - so you don't need quite so much attack boost to make it a "fair" fight.  Arctic Orangery crit can also help tilt things in your favor. 1-8 Champions + 0-7 Rogues - If you're a defense stacker Champions have higher stats than Assault Tanks and may take even less damage. 8 Strike Teams or Attack Helicopters - Move first + hit first.  Not usually overly impressive in this age, but can help in places.  Note that Attack Helicopters only move first if the defense has no Strike Teams.	+ Contact! + Rogues are a powerful combination + Can get very advanced troops - not so obscure this time, but you should still do your research if you're planning on it - it's important to have as many unresearched techs as possible if you want to get far, and map decisions matter in some places. + Missile Artillery on defense is pretty safely ignorable to some extent due to "One Shot".  AI also usually does not make good use of MIRV. + Flying is a powerful new ability even if it's not often important yet due to the issues with the in-age artillery.
Tomorrow Era	2-8 Combat Drones + 0-6 Rogues - Rogues absorb unavoidable hits in first round of combat.  Combat drones blow *anything* up in 2 hits while ignoring artillery.  For best results, fight manually - but you can auto a great number of fights with them as well.  Their biggest issue is many Stealth Tanks as they'll take retaliation when hitting them. 1-8 Stealth Tanks + 0-7 Rogues - Good against most things - main problems are enemy Stealth Tanks and Ultra APs as you get up in attrition as they'll both get in some painful retaliation.	+ Combat Drones have *crazy* high attack.  Easily can abuse them against most armies to hit significantly higher attrition than possible in other ages with similar boost. + Stealth Tanks are a generally useful Hiding unit  - Defending armies with many Stealth Tanks are difficult to deal with.  At low-medium attrition you can use Microwave Blasters.  At medium-high attrition I recommend *carefully* using some OF story troops like Sub Cruisers or Hydroelectric Eels in combination with Rogues.
Future Era	1-8 Hover Tanks + 0-7 Rogues - Best you've got against pretty much anything.  Other armies can be used against some things as minor improvements.	+ Hover Tanks do everything - Nothing handles 3+ Hover Tanks on defense acceptably at medium attrition.  You have to start cherry-picking fights to change out tough fights instead looking for the easy ones.  Not good if you're just trying to power through a specific sector! - 2 units are utterly useless (Satellite Spotters + Drone Swarms) and 1 autos poorly (Exoskeleton Soldier)
Arctic Future	1-8 Battle Fortresses + 0-7 Rogues.  Reactive Armor 3 means your units are automatically pretty tanky taking 4 hits to die without any investment in defense.  Can reach relatively high attrition even if it's not ideal for many things.  Arctic Orangery can help with the mirror (We both do 3 damage to each other normally; but I can crit for 5 and save a shot!) 2-8 Plasma Artillery + 0-4 Rail Guns + 0-4 Battle Fortresses + 0-4 Rogues.  So this looks rather like many armies but the concept is rather straight forward: Plasma Artillery deliver the beats and can fire every turn unlike Rail Guns from FE, but they can't do more than 3 damage to a Battle Fortress (so you may want some Rail Guns to help blow through that), and they can't shoot flying things (so you may want some Battle Fortresses for that - Rail Guns can help a little with that too - but only every other turn).  And you may want to fill in some slots with Rogues to absorb some unavoidable hits. 4-8 Combat Drones or Dragon Drones + 0-4 Rogues - Takes advantage of many Plasma Artillery on defense.  Combat Drones are easier to use, and *still* have enough attack to be relevant (and more than Dragon Drones on that note)  But they can't crit and occasionally Dragon Drones' multi-hit ability is useful - especially if you fight manually. 8 Recon Raiders - Move first + hit first.  As long as there's not too many Battle Fortresses on defense, you've got a good shot. 1-8 Hover Tanks + 0-7 Rogues - As long as there's not too many Plasma Artillery on defense; Dragon Drones are squishy, and stealth is reasonably effective against everything else.	+ Good all-round age with many useful army setups - Some strange units that have stats that hardly seem fitting for the age - Battle Fortresses on defense are going to be bloody
Oceanic Future	4-8 Turturrets + 0-4 ? + 0-4 Rogues - Similar to the Plasma Cannon arrangement in AF, this bumps up to be the most important army in OF due to the power of Mortar.  In addition to the things that Plasma Artillery cannot hit, Turturrets cannot hit stealthed units.  So ? may be C.R.A.B. Mechs to take out an eel or it may be Plasma Artillery if range is deemed important or it may be Sub Cruisers as a generally decent all-round unit from the age. 4-8 Gliders + 0-4 Rogues - If there's many artillery on defense and you can't out-artillery them for some reason.  There's finally a proper upgrade to the TE Combat Drone to get the AO crit back - its attack stat is not nearly so impressive compared to OF defenses though, and it loses a bit in attack range that might make it harder to hit the precise thing you want on the first turn. 1-2 Sub Cruisers + 6-7 Rogues - Can retaliate against anything but the artillery and Scimitars reliably - and Medusa can't move and are generally exposed at the start - mostly it only needs to avoid Turturrets 8 Hydroelectric Eels - There's many bushes on the OF battlefield to hide in.  You can generally plan to hide your entire army and pick off the enemy; watch out for the few enemy anti-stealth units.  Mostly a manual-battle strategy. 1-8 Hover Tanks + 0-7 Rogues - Stats are a little low, but Hides on Plains is still a very powerful ability to compensate - most anti-stealth units in age are highly limited.  Defense may also still be relevant in combination with the stealth as its not that far behind the in-age Force Field unit.  No Rogues is sometimes desirable to not catch splash damage from Turturrets transforming your rogues.	+ Solid answers for any army + Good Contact! unit + Powerful artillery with new Mortar ability + Decent Flying unit + Decent Hiding unit - Despite a very diverse slate of 10 units, most of them are just novelties and not all that useful
Virtual Future	4-8 Rocket Troops + 0-4 Rogues - Turturrets taken to the extreme against an age with weaker overall units.  Works well against everything but Ninjas.  Mortar is absolutely devastating.  No flying unit in-age to fear. 8 Ninjas - Move first + hit first 1-8 Ronin Bots + 0-7 Rogues - Force Field can help augment your defense to make them continue to feel durable if you haven't completely ignored it.  No amount of defense will make them feel good against any amount of Rocket Troops though.	+ Rocket Troops rock - Ninjas on defense are a pain - 2 units are pretty much useless
Space Age Mars	8 Sentinels - Move first + hit first + avoid any artillery.  Great against lots of stuff.  Your bread & butter army. 8 Rocket Troops - Mortar is still an awesome ability and Steel Wardens are so slow that VF Rocket Troops can win against a Max-Attrition 12000% boosted 8 Steel Warden Defense - even with no boost of their own to speak of!  Also usable against small amounts of other ground troops.  Tesla Walkers having the same initiative can mix in if you see a use for them in a fight. 2-4 Steel Wardens + 4-6 Rogues -  Force Field can help strengthen any investment you've put into defense.  Not bad all round units. 2-4 Sniperbots or Tesla Walkers + 4-6 Rogues - they're not bad units per se - but not really necessary either.  Occasionally they might be a minor improvement over one of the other armies.	+ Great fighting age with reasonable answers for anything  + Potential for super-high-attrition crazy setups either taking advantage of Flyers + AO Crit vs artillery or Rocket Troops vs slow things.
Space Age Asteroid Belt	4-6 Nail Storms + 2-4 Rogues - Pretty good against most things - can get bloody if there's many Nail Storms on defense - especially if one of them makes it to rubble. 8 Sentinels - Move first + hit first - Yup, still.  Now without AO crit.  For the toughest fights this is what I've had the best luck with. 2-6 B.E.L.T.s + 2-6 Rogues - can handle Nail Storms that make it to rubble better than most things - can't hit Hover Hammers though. 2 Hover Hammers + 6 Rogues - generally not as good as Sentinels - but you'll be winning a bunch of Hover Hammers from GE, GBG, Events, etc and against some of the B.E.L.T. heavy defenses these are usable to save you some Sentinels for when you need them. 8 Rocket Troops - can still handle 8 Shredders akin to SAM but struggles more with other stuff mixed in - mostly due to higher base stats.	- No good answer for 8 Nail Storm defenses at medium-high attrition.  Hoping for good damage rolls from SAM Sentinels and Keen Eye procs is generally your best bet.  Manual battle is recommended so you can bail if you get bad rolls before they get a chance to destroy your Sentinels. - Most units are pretty useless

Fighting GE4 : Getting troops ahead of your age from the continent map

Alright, so in many ages fighting GE4 largely seems like an impossibility (others are not so bad) - one way to tip the scales beyond ridiculously levelled GBs is to fight ahead of your age on the continent map and win units from story quests.

Update (07/01/21): Fleshed out the later age possibilities.  Apart from trying to get FE+ troops in PME you should generally not let map or tech get ahead of story, and save as many optional techs as you can.

1) Iron Age - Obtainable (2) Armored Infantry : If you complete the story up to the point where you unlock the EMA bonus area (barbarians), and finish the bonus questline, the final reward is 2 armored infantry.  How much does this help?  Well it'll make fighting through difficulty 3 a breeze - but 4 might still need significant boost and care not to lose your precious unattached units.

2) Late Middle Ages - Obtainable Grenadiers, Musketeers, Field Guns : If you complete the LMA story it unlocks the LMA bonus area to the south.  At various points along the way this questline rewards Colonial Age troops.  To finish it entirely you will need to research the tech for Cannons - but some of the units are available very early.  How much does this help?  Some...  I'm not sure it's enough to fight 4 without losses so as with iron age some care may be required not to lose your precious unattached units.  I've heard someone say they got Jaeger Infantry (Industrial Age) in LMA and that would make things a breeze - but I can't see how that's possible as Colonial Age story has quests that require construction of Colonial Age buildings.  Only thing I can imagine is unlocking the Industrial Age bonus area but as far as I know those don't reward units.  (Note if trying that, you cannot finish the Industrial Age bonus questline and get that quest slot available for other quests again without Modern Roads (Industrial Age))

3) Colonial Age - Obtainable All Industrial Troops, Conscripts OR 1 Rapid Fire Cannon + 2 Snipers + 1 Armored Car.  The Industrial Age troops are relatively straight forward to do and enough to fight most of GE4 without difficulty combined with rogues.  The progressive era troops you have to enter Colonial age with it in mind that you're going for them.  There are a number of quests that will request things like 'Build a Residential building from the Industrial Age OR Research a tech that unlocks a residential building' so you'll need to save as many techs as you can to make sure you can fulfill that option.  In doing the Industrial Story, you should note there are 4 ways it can progress: Support the South, Support the North, Fight both, Peace.  I recommend supporting the South (fighting only the northern provinces).  The combat might be a little more challenging but you can complete the story without unlocking the bonus questline and maintain your extra sidequest slot til you're ready.  It also gives you a nice mix of all Industrial troops (I can't say for sure what troops exactly you get in the other route).  When it comes to Progressive Era, you again have the same sort of options.  Peace gives you conscripts.  Fighting the germans gives you the RFC+snipers+car.  I believe fighting the brits gives the same troops.  The good news : either progressive era troop option should be plenty to breeze through GE4.

4) Industrial Age - Obtainable PE, ME, PME troops - Most notable is the MG team from PME.  To get these it's important to stay at peace with Che Guerrero, and not to finish his last territory for as long as possible.  This will give you "Business with Che" quests which will reward you with MG teams.

5) Postmodern Era - You can get a few CE troops "normally".  There's also a method to skip the CE blocker quest in PME and get to the advanced troops listed under CE...  I've not done it myself to recommend it but the gist is that *before* finishing PME story quests you skip way ahead on the continent map, working your way through to FE map.  Once on FE map you start catching up on story and it'll bypass the CE blocker hopefully.  There are more details on this elsewhere - look around if you're interested :)

6) Contemporary Era - If you've skipped enough technologies, you can get through to OF quests here.  FE Hover Tanks are perhaps the most notable troop at this point - to get 4 Hover Tanks instead of 1 you should negotiate with Joy Danba at the start of FE story - then when you meet her again later in the map she'll give you 3 Hover Tanks.  An OF quest requiring you to finish productions in an OF production building acts as a final block preventing you from getting any further troops above your era.

7) Tomorrow Era - You can certainly finish whatever you didn't in CE here in getting to that OF blockade.  OF Sub Cruisers I find quite useful in TE.