What became critical to protecting what blacks were achieving?

The 13th Amendment, which was ratified in 1865, abolished slavery. Three years later, the 14th Amendment provided blacks with citizenship and equal protection under the law. And in 1870, the 15th Amendment gave black American males the right to vote.

Explanation:

it would be

the treaty of brest-litovsk was a peace treaty signed on 3 march 1918 between the new bolshevik government of russia and the central powers (german empire, austria-hungary, bulgaria, and the ottoman empire), that ended russia's participation in world war i.