In Vietnam, Operation Jay began about 30 kilometers northwest of Hue, and lasted nine days. The 2d Battalion, 4th Marines landed north of the North Vietnamese 812th Main Force Battalion, and the 2d Battalion, 1st Marines landed south of the enemy's position. Caught in between the two Marine units, the enemy suffered over 80 dead in nine days of fighting.

Shortly before dawn, eight divisions of the North Korean People's Army crossed the 38th Parallel and invaded the Republic of Korea. Within three days, the South Korean capital city of Seoul had been captured. On 30 June, President Harry S. Truman ordered a naval blockade of the Korean coast and authorized the sending of U.S. ground troops to Korea. Two days later, General Douglas MacArthur, the Commander in Chief Far East, formally requested that a Marine regimental combat team be deployed to the Far East.

BGen James G. Harbord, the Commanding General of the 4th Marine Brigade, notified American Expeditionary Force Headquarters that Belleau Wood was "now U.S. Marine Corps entirely." After 20 days of combat, and at a cost of over 4,000 casualties, the 4th Brigade of Marines had proven its fighting heart. The grateful Commander of the French Sixth Army would soon decree that in all official correspondence, Belleau Wood would henceforth bear the name, "Bois de la Brigade de Marine."

At dawn on this date, the crack German 28th Division attacked along the axis of the Paris-Metz road hitting the American 2d Division, including the 4th M

The Battle of Midway began. But the 6th Defense Battalion had been on the island for nearly 6 months. Upon hearing of the attack on Pearl Harbor, they immediately went to general quarters; however, no attacks transpired that day. That evening, two destroyers from the Imperial Japanese Navy, the Sazanami and Ushio began shelling the atoll for 23 minutes. One 5-inch battery from the 6th Defense Battalion engaged the destroyers during their second run until they departed the area. During this engagement, First Lieutenant George H. Cannon was mortally wounded; however, he refused evacuation while reorganizing his battery's command post. For his actions he was posthumously awarded the Medal of Honor. In total, ten marines from the battalion were killed in action and an additional ten more were wounded in action.

On 2 May 1942, Admiral Chester W. Nimitz spent the entire day at Midway inspecting the island. He spent a great deal of time with LtCol Shannon and inquired about what his defense battalion required in order to repel an amphibious assault. LtCol Shannon also assured Nimitz that if properly supported he could hold the island. Upon returning to his headquarters at Pearl Harbor, Admiral Nimitz wrote a joint letter to LtCol Shannon and Commander Cyril T. Simard, Commanding Officer of the Naval Air Station. He instructed both that they had been spot promoted to Colonel and Captain respectively, their garrison would receive his full support and he also let them know that he had intelligence that Midway was going to be attacked by the Japanese at the end of the month. Shortly thereafter, five additional antiaircraft batteries from the 3d Defense Battalion reinforced the island along with two companies from the Marine Corps' 2nd Raider Battalion. Battalion strength had swelled to nearly 1700 personnel by early June 1942. by At 0555 on the morning of 4 June 1942, 6th Defense Battalion's SCR-270 early warning radarpicked up a large force of Japanese aircraft approximately ninety miles out and approaching from 320 degrees. Thirty-six Japanese bombers eventually made it to Midway in two waves and were engaged by the guns of the reinforced battalion. Japanese after action reports detail l

A Marine tactical recovery team from the 24th Marine Expeditionary Unit stationed on board the USS Kearsarge rescued a downed U.S. pilot, Captain Scott O'Grady, USAF, from Bosnian-Serb territory in Bosnia.

The First Marine Battalion, commanded by LtCol Robert W. Huntington, landed on the eastern side of Guantanamo Bay, Cuba. The next day, Lt Herbert L. Draper hoisted the American flag on a flag pole at Camp McCalla where it flew during the next eleven days. LtCol Huntington later sent the flag with an accompanying letter to Colonel Commandant Charles Heywood noting that "when bullets were flying, ...the sight of the flag upon the midnight sky has thrilled our hearts."

President John F. Kennedy signed a Presidential Proclamation calling for the American flag to be flown at the Marine Corps War Memorial in Arlington, Virginia, "at all times during the day and night." Discussions between the Attorney General's office and Marine Corps officials earlier in 1961 on improving the visibility and appearance of the monument led to the proposal to fly the Flag continuously, which by law could only be done by Congressional legislation or by Presidential proclamation.

Flag Day commemorates, when the Continental Congress determined the composition of the nation's banner: “Resolved, That the flag of the thirteen United States be thirteen stripes, alternate red and white; that the union be thirteen stars, white in a blue field, representing a new constellation.”

Preceded by naval gunfire and carrier air strikes, the V Amphibious Corps assaulted the west coast of Saipan, Marianas Islands. By nightfall, the 2d and 4th Marine Divisions, moving against heavy opposition, had established a beachhead 10,000 yards wide and 1,500 yards deep.

The 24th Marine Expeditionary Unit returned to Mogadishu, Somalia, to stand ready to assist United Nations forces in maintaining peace in the war-torn country. Earlier that month, the 24th MEU had been ordered to cut short Exercise Eager Mace 93-2 in Kuwait to respond to possible contingency operations in Somalia.