Question

what power does the constitution give the president in the area of war

Answer 1

Here is an excellent site:

http://www.law.umkc.edu/faculty/projects/ftrials/conlaw/warandtreaty.htm

Answer 2

Congress (the legislative branch) is the only agency that has the constitutionally derived authority to declare war on another country. Look up the War Powers Act of 1973 and look at the actual text of the Constitution itself.