I don't think it slowed down the Soviets much - Andrei Sakharov seems to have worked out the staging approach pretty quickly after seeing the results of analys

I don't think it slowed down the Soviets much - Andrei Sakharov seems to have worked out the staging approach pretty quickly after seeing the results of analysis of the Castle Bravo test (i.e. the first one to use lithium deuteride).