There's bad shit happenin' in central Asia. Falling stars and all that shit.
Then the reports start coming out...
Ahem.
Anyway! An Imperial Guard regiment, roughly 3 million in number with the appropriate number of tanks, artillery and armoured vehicles, has landed in said location (vaguely around... Tajikistan I guess, between Russia, China and the Middle East). They know they're on Holy Terra; their mission is to conquer the world that it may be ready for their Emperor when He appears.
Their transports were heavily damaged in the warp storm that flung them backwards through time, and the Navy escort craft were destroyed as well, so orbital bombardment is not an option; however, they have a goodly supply of weapons and ammo in the transports, which they brought down planetside. They also have a small supply of Lightnings and Marauder aircraft.
Against them are the Russian, Chinese, and an EU army, as well as whatever forces are available to the countries in the region; due to various reasons the US is not involved.
Who comes out ahead?
B.) Same as above, but this time, the American military is involved.
I'd have done it with Space Marines, but that'd have been a bit extreme...

Edited to add aircraft