What events of 1949 thrust the cold war into a new and seemingly more dangerous stage

The Russians successfully detonated their first atomic bomb.  This starts the arms race between the U.S.A. and the U.S.S.R.  It made nuclear warfare a possibility that frightened many people at the time given how an atomic caused devastation in Hiroshima and Nagasaki.

jewish people, gypsies, and political opponents.

this is a good question! i'll do some research and come back when i have the answer!