system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why doesn't the West openly say the Russian military is fighting in Ukraine?
gpt
West excluding Russia: not enough evidence.

Russia's military doctrine is called 'maskirovka', and revolves around deception. It's a tactic that has been used for approximately a millennium, and is still as effective as ever. Basically the Russians deny everything, admit nothing, and play dirty; for example there is some evidence that they painted trucks white, disguising them as an aid convoy, and used them to ship ammunition and soldiers into Ukraine. 

Any other nation would probably admit that they have invaded another country, but Russia's MO is deception, disguise, and denial.