The formal name for the Battle of Iwo Jima was Operation Detachment. Its goal was to take the island and deprive the Imperial Japanese Army the use of its two air bases, both a salient aimed at Allied territory, and an untaken fortification behind lines.
The cost was immense: 4,000 American lives, and tens of thousand of Japanese. But there's another cost associated with war, and that's the cost of planes, ships, equipment... and they had to be paid for. So the US Department of the Treasury issued this very short film as part of the Seventh War Loan. While celebrities of all sorts made speeches, this played in the movie theaters.