Will losing a strategic resource disband units?

Question

Does losing a strategic resource make a military unit any less effective, disband them, or else? Or is there no negative effect?

I ask specifically thinking about strategic resources I gain via trade agreements. If I get some oil for example for 90 turns from another civ, and I build planes with that oil, after the 90 turns if the other civ does not renew the trade agreement, do I suffer?

I found this similar question, but it's about buildings instead of units. I could not find anything definitive online that suggested the actual consequences.

In Civ 5, do buildings get any penalties when you lose a source of needed strategic resource?

Answer 1

If you have more units that depend on a strategic resource than you have of that resource, you will suffer a significant combat penalty, see the "Strategic Resource Penalty" line item below:

In this case, you will see a negative number on the top status bar by the strategic resource you are lacking. It does not matter how your strategic resources get into the negatives - you can have a trade deal expire, lose territory, or have an improvement pillaged, the effect is the same.

50% lost strength is a severe penalty - it makes these units worse than contemporary units that don't require resources (ie, it makes a Swordsman worse than a Spearman) and can even make the unit weaker than units of previous eras.

The quantity you are over doesn't seem to matter, either. You can be -1 or -5 with the same 50% penalty. I tested this just now on a hotseat game between two players that were running different difficulty levels. The difficulty level did not seem to impact it either. Further, I tried two different units, a Swordsman and a Roman Legion and both had the same penalty applied.

Another side effect of going into the negatives is that any unit you were building that depends on that resource will immediately cancel. When I reconnected the strategic resource, I was able to resume production where it left off.

I don't believe patch or DLC matters, but for the record this was in a game with all the current expansions/DLC (Civ5 Gold, Gods and Kings, Brave New World) available.

Answer 2

No, I believe strategic resource dependent units will function at half strength until the available quantity of a particular resource is greater than or equal to the number of units that depend on it.

From Civ 5 wikia site - Resources:

On the other hand, if the civilization loses access to some of the strategic resources they are currently using, and find themselves using more than they're producing or trading, then military units depending on the resource in question will fight with a large combat penalty, until the situation is remedied.

This 2K Forum post seems to confirm that the penalty is 50%:

Sometimes I see enemy units feature a -50% strategic resource penalty in combat.

Answer 3

The -50% doesn´t necessarily mean half combat strength. Civ 5 has a big inconsistency problem with percentage boosts, they are added together before actually being implemented, I think.

In case of building boosts that makes sense and also keeps a lot of things from getting too overpowered, imagine a City with University (and Rationalism), Research Lab, National College and Observatory, each plus 50% for a total of 200%, equaling 3x Science versus that being multiplicative 1.5^4 ~ 5.06x Science, anyone not getting a mountain would be scientifically screwed compared to other civs that have one

However this seemingly also applies to combat strength, which often doesn´t make things as worse as losing half the combat strength, I think that plus 50% and -50% cancel each other out, instead of halving your strength and then adding 50% of that (equaling 75% of originial combat strength).

I´m not 100% sure, but if that applies, in a lot of situations, this will be just a minor inconvenience, for example Rocket Artillery (requires Aluminium, without promotions) attacks City: Because it is a siege unit, +200%, then -50% means +150% remains, which just reduces your final multiplier for your Rocket Artillery from 3x down to 2.5x. Now in case of a Rocket Artillery defending (even against cities, that 200% only counts on offense), that would be halved, but the RA can stand outside the city and if you can protect your RA, you have a very minor downside.