On Okinawa, Marines of the III Amphibious Corps continued to make good progress all along their front, clearing Zampa Misaki and seizing the Katchin Peninsula, thus effectively cutting the island in two. By this date (D+2), III AC elements had reached objectives thought originally to require 11 days to take.
Five Marine guards were killed and eight wounded when attacked by Communist Chinese raiders near the Hsin Ho ammunition depot in Northern China. This last major clash between Marines of the 1st Marine Division and Communist forces occurred shortly after withdrawal and redeployment plans from China were issued for the 1st Division and 1st Marine Aircraft Wing on 1 April.
Lieutenant Colonel John H. Glenn, Jr. was named as one of the original seven Project Mercury astronauts selected for space training. The seven astronauts, all volunteers, were selected by NASA from an initial group of 110 leading military test pilots. Three years later, on 20 February 1962, Col Glenn would become the first American to orbit the Earth.
Marines of the 4th Brigade suffered their first gas attack on the night and early morning hours of 12-13 April when the Germans bombarded the 74th Company, 6th Marines near Verdun with mustard gas. Nine Marine officers and 305 enlisted Marines were gassed and evacuated, and 30 Marines died from the effects of the gas shells which hit in the middle of the reserve area cantonments in which they were sleeping.
Marine Corps operational involvement in the Vietnam War began on Palm Sunday when HMM-362 with its Sikorsky UH-34s arrived at Soc Trang in the Delta south of Saigon. The task unit was called "Shufly" and its first operational employment involved lifting Vietnamese troops into battle.
One Marine Security Guard was killed and seven were wounded when a large car bomb exploded just outside the U.S. Embassy in Beirut, Lebanon. Lance Corporal Robert McMaugh was standing guard at Post 1, just inside the front entrance when the bomb exploded outside the door. The explosion killed 61 people including 17 Americans. LCpl McMaugh was buried at Arlington National Cemetery on 26 April.
Marine carrier-based airplanes made their first aerial contact with enemy planes over the Korean front lines. Captain Philip C. Delong shot down two YAK fighters and 1st Lieutenant Harold D. Daigh destroyed one more and damaged another in the heavily defended Pyongyang-Chinnanpo area. Both pilots were with VMF-312 flying from the USS Bataan.
First Lieutenant Presley N. O'Bannon, who with seven other Marines was part of a force of Greeks and Arabs led by American Consul William Eaton, raised the United States flag for the first time over a conquered fortress of the Old World at Derne, a stronghold of the Tripolitan pirates. Two Marines were killed and one wounded in the assault on the walled city.
The last A-6E Intruder departed from Marine Corps service. Marine All Weather Attack Squadron 332 transferred the last Marine A-6E to St. Augustine, Florida, and prepared for the squadron's transition to the F/A-18D and eventual movement from Cherry Point to Beaufort, South Carolina.