During World War Two, island assaults required amphibious vehicles that sometimes needed to cross coral reefs on their way to the beaches. The US Marines had a range of specialised amphibious Alligator LVT's (Landing Vehicle Tracked) available, which were developed from a hurricane rescue craft designed by John A. Roebling before the war. LVT's were first used at Guadalcanal in 1942.
The LVT(a)-4 was a version that carried a small howitzer to provide close infantry support during and after the landings. Being tracked meant that LVT's were particularly useful in the Pacific - they were well equipped for crossing coral reefs, other craft had to avoid such obstacles or risk becoming stranded.