[sornaensis]

Hitler had (poor) intelligence that the Soviets had thousands of tanks (they actually had more than the germans thought); he refused to believe that such a 'backwards' country could have such a strong modern military however.

[seanw444]

There's a decent chance that without US assistance, that wouldn't have been the case. We sent them a lot of equipment.

[meepmorp]

Just to expand on that - we sent multiple millions of tons of aid - probably $120-150 billion, in current dollars. Thousands of tanks, thousands of planes, plus trains (locomotives and cars), food, fuel, anmmo, explosives, and industrial supplies. Not to minimize the tremendous price the Soviets paid in lives (soldier and civilian), but they almost certainly would've lost the war without lend-lease.