They were four United States Army chaplains who gave their lives to save other civilian and military personnel during the sinking of the troop ship USAT Dorchester on February 3, 1943, during World War II. They helped other soldiers board lifeboats and gave up their own life jackets when the supply ran out. The chaplains joined arms, said prayers, and sang hymns as they went down with the ship.
The four men were relatively new chaplains, who all held the rank of lieutenant. They included Methodist minister the Reverend George L. Fox,
Rabbi Alexander D. Goode,
Roman Catholic priest the Reverend John P. Washington, and
Reformed Church in America minister the Reverend Clark V. Poling.
You can read more about their story on Wikipedia
and the Four Chaplains Memorial Foundation