What are the advantages and disadvantages to purchasing land rather than conquering it?

Question

In many parts of the world that we have explored so far, lands were acquired by means of warfare. Much of the land in America was purchased from other nations.

Answer 1

If you conquer it you have more enemy's.

Answer 2

The big advantage in purchasing is that you are not liable to get yourself killed over the transaction.Louisiana and Alaska  were two prime examples of purchase and the original owners sold because they were in a tenuous position. New Mexico, California  and Hawaii are examples of the use of force. It´s all a question of expediency.