I remember in earth 2025 allies send 25% and no more than double this type of units.
But it seems here is double all def/att.
If country A has
0 troops
1000 jets
0 tanks
Country B (allied) has
1000 troops
0 jets
0 tanks

What will be att power? 1000 jets or 1125 jets? (it was 1000 in earth2025)

Same question for def.

It doesn't matter what units the ally has, only offensive/defensive power.

If country A sends all 1000 jets, that's 2k offense points meaning the max total help from ally is 2k.

Country B has 1000 Troops which is 1k off points and can help with 25% of that which is 250.

The attack will have offensive power of 2250 points which is equal to 1125 jets.

Same goes for def. It's power based, not unit based.

this thread http://forums.earthempires.com/...is-o-ally-strength-calc-d has alot answers.