A little more on the Russian tanks sent to Spanish communist Republicans by Joe ( no checks - just cash) Stalin. They were gassers. Yes, Spain had refineries in the 30s, but Spanish gasoline was crappy & quickly fouled spark plugs on the tanks.
Sometimes while said tank was clattering into battle!
What to do? Rock - paper - scissors to see who climbs out to clean & re-gap the spark plugs? No - everybody bailed and beat feet! The tanks then became artillery targets.
Further compounding the tank trouble was what Franco's Nationalists got as aid from Germany and Italy. Tanks? Nope - anti tank guns! The commies only had three tanks still in service when the civil war ended.
The commies were idealistic and dedicated to their cause, but the Nationalists had the military. One of the first things the commies seized was the banks. Stalin was quick to perceive this and got them to pay for their aid in gold. Like the gold from the new world = Mexico and South America. All those Spanish treasure ships that made it back to Spain had actual tons of gold.
Stalin drained them of it, and Spain is poor to this very day for that reason. The gold lays shining and collecting dust in Russian vaults.
Once again, I should leave well enough alone. I researched the topic for an article I wrote for "ARMI e' TIRO", an Italian gun magazine & still have my notes. The publisher sent copies & it was an odd feeling to see my name at the top & not be able to read it! I doesn't speak Italian. SW