A civilian army never wins a drawn out war. Wales fell to some English king that way, Henry VIII maybe? Anyhow, he starved them out. They lost.
Overall, Swat is right, you're just making a last ditch effort that really, in a realistic scenario, would have ended a while back, and would be history by now. And as to your army of however much, you don't seem to have taken any casualties, or are just making up crap about the numbers.
Avalonia's barbarian army (which has no sympathy for Slainte, as Slainte allied itself with Caprica which opressed the barbarians) is reinforced with warriors from the fighting tribes of the far side. They have undergone basic training, and provide a ferocious supplement to the average barbarian. The army continues to march into Slainte, leaving a bare plain of scorched earth behind it.
I didn't even know Russia was in WWI. Guess they didn't make too much of a difference.