On 16 February 1945, the 503rd RCT jumped on Fortress Corregidor ("the Rock") to liberate that island from occupying Japanese forces. Braving intense fire, the paratroopers rushed forward and overcame the heavy blockhouse defenses, dropping explosives into embrasures to kill hidden Japanese gunners. For its successful capture of Corregidor, the unit was awarded a Presidential Unit Citation and received its nickname, "the Rock Regiment" from it. The regimental insignia was designed by Private First Class Thomas M. McNeill while recuperating from his injuries and dengue fever, hepatitis, and malaria on Mindoro Island, following the battle of Corregidor.