I am under the belief that "Z" was painted on military vehicles transiting to be part of the pre-war buildup on Russia's western border. "Zapad" being Russian f

I am under the belief that "Z" was painted on military vehicles transiting to be part of the pre-war buildup on Russia's western border. "Zapad" being Russian for "West". I don't know this to be true but it seems plausible to me. I'm sure there are plenty of co-opted uses/meanings of the "Z" now though.