Nation States, currently192 of them recognized by the United Nations, maintain the rights to defend themselves with military force. With lots of nations integrated close together in commerce, there's less motivation to go to war with their neighbors, making life safer. It's just expensive to upkeep a military, and offers no commercial benefit if you're feeling safe with your neighbor. Some nations back each other up with statements of mutual defense. Demilitarization occurs.
The African Americans responded by coming in great numbers to volunteer in the Union War.
Francisco Pizarro was a Spanish conquistador who conquered the Inca Empire in Peru. He had captured and after that killed Incas Emperor Atahualpa. With his army of 500 Spaniards he entered Incas capital of Cusco in 1533. Ather he had destroyed Cusco, Pizarro founded a new capital of Peru, Lima in 1535.