You are the chief support of the US army as of now. Your base is under attack from the enemy soldiers who only seem to grow in power wave after wave. You cannot afford to take a nap while on guard because the defense mission continues for 19 long days. Hold the fort each day by shooting and bombarding all the enemies who will show no sign of retreat. The money earned after the completion of each level can be used to purchase new and more powerful weapons that will prove to be very useful during the combats.