Why are the thirteenth, fourteenth, and fifteenth amendments called the “civil war amendments”?

The Fourteenth Amendment (proposed in 1866 and ratified in 1868) provides a broad definition of national citizenship, overturning the Dred Scott case, which excluded African Americans. It requires the states to provide equal protection under the law to all persons (not only to citizens) within their jurisdictions.
The Thirteenth Amendment (proposed and ratified in 

The Fifteenth Amendment (ratified in 1870) grants voting rights regardless of "race, color, or previous condition of servitude".

1865) abolished slavery.

Andrei karlov was the russian ambassador