Declare war on the Islamic state

The US should not stand by as people are executed in horrific ways by the Islamic State. Several US citizens have already been executed. If the United States were to declare war on the islamic State it would end the killings brought on by Isis. During World War II Hitler killed millions of people before the 1944 which was when the United States joined the war. It only took one year for the war to end and all killing of jews in concentration camps to cease. This was a war with a whole country. If the United States want to be known as liberators then we should declare war and create a campaign which would consist of retaking cities under Islamic State control.