Wrong, they didn't want to field their own army. And, in fact, no one in their right mind wanted them to. The reason this whole thing was a mistake all the way back to 2008 is that the insistence of the U.S. to expand NATO right up to the back yard of Russia made a possible conflict between them all the more likely. And we DON'T want a conflict between U.S. and Russia. The U.S. doesn't really care about Ukraine. It can use it as a proxy army, as you say, and any losses inflicted on Russia is a gain to them, something that they didn't even bother to hide.

I'm far from a fan of U.S. militarism, but in a conventional war against the U.S. army I think that Russia wouldn't stand a chance. However this is the last thing we'd want to put to the test. Forget about guerillas hiding in caves. When fighting against the Iraqi army the U.S. curb-stomped it with ease and most of the losses it suffered were from friendly fire. Russia is not Iraq, of course, but the war in Ukraine has proven that it suffers from serious logistics problems and that it relies on obsolescent tech or worse for the bulk of its operations. You can argue that the U.S. military is bloated and its toys cost much more than they're worth, but it's still more formidable than any other until proven otherwise.