Trade your Units

Why you cannot give your allys Units like ressources?
This would be not such waste of resources when you kill your people, because you need another Unit more and an ally could use this Unit. Than he could the Unit and the paid ressurces are not wasted.

???
why dont you just send your units to them and fight there?

Because this would not have any effect on the population limit. Or the ally need Villagers and you have to many.

This would probably end up taking away too many bonuses of civs, since you could easily just trade Hittite catapults with your Egyptian ally etc.

Right now, you can still do that by using priests and being neutral with ally to convert units, or, you can use the tribute system to send resources to them after using your own villagers to collect the resources.

@“teutonic tanks” said:
???
why dont you just send your units to them and fight there?

There are plenty reasons…
They don’t want waste units, may be one player need a specific counter…etc etc