Did Polk instigate the war with Mexico? If so how did he do that?

What Polk wanted was to push Mexico into negotiating with the United States, and he was willing to create a threat of war to do this. If he had to fight, he wanted a short war and a quick victory. He never expected a long-drawn-out war. The Army was not ready for war and had never fought so far from home before. The country was divided. So Polk was taking a considerable risk in his bold stand toward Mexico.