Why did russia sign a non-aggression treaty with adolf hitler

I assume that you refer to the Ribbentrop-Molotov pact  between Russia and Nazi Germany before the war.

Officially, they claimed that it offered both countries safety: non-agression treaties generally offer safety to both countries.

Unofficially, it allowed them to divide the European land between them among the two, which they later did in 1939.

Acase involving the laws of a single state.

African americans at the time just came out of slavery and needed money to provide for there families. so they joined for the money mainly.