It is isn't, the minor issues that affected Cossacks are far worse in this game, making it impossible without cheats.
First off the cpu opponent does not need resources, so cutting off their supplies is pointless.
Secondly, the cpu can build an indefinite number of troops and sends them at you constantly.
This brings up a major issue: this isn't like WWI in anyway (other than hopelessness) and the inaccuracies are awful. Furthermore, tanks are highly unbalanced and overpowered and planes out right suck. The only way to beat some levels is to build a wall of defenses and inch by inch getting to the other side and killing the enemy. This game lacks any form of depth.
Play it only if you want a laugh at how this game was even released.
It is a shame that it is one of a few games sent in this conflict.