A political party can not start a war, only "congress". and the congress is never one party, it will alway come to about 40-60 demacrats/republics each, and most of the time any where from 1-5 other thrid parties or indepences(there is a 100 members of congess total). Also the president can send small amouts of troops over our boarders because he is in charge of forgin affairs.