19 April Elements of the 1st Air Cavalry Division, the 101st Airborne Division, and several ARVN units begin Operation Delaware/Lam Son 216. This operation takes place in the A Shau Valley and is designed as a spoiling assault to disrupt enemy preparations for another attack on Hue.
30 April NVA units are engaged in the village of Dai Do by BLT 2/4. Heavy fighting in this area continues until 3 May. 4 May The 7th Marines begin Operation Allen Brook, an operation designed to
disrupt the growing enemy presence South of Da Nang.
30 April-17May Marine, Army, and ARVN units succeed in thwarting a possible enemy assault on Dong Ha. The NVA suffered a reported 1,547 casualties while the allies sustained casualties of nearly 300 dead and 1,000 wounded.
4 May The 7th Marines begin Operation Allen Brook, an operation designed to disrupt the growing enemy presence south of Da Nang.
5 May Signalling the second major offensive of the year, enemy troops launch 119 rocket and mortar attacks on towns and cities throughout South Vietnam.
13 May Peace calks among North Vietnam, South Vietnam, and the United States begin in Paris.
17 May Operation Delaware/Lam Son 216 ends with a reported 735 enemy casualties with 142 Army personnel killed and 731 wounded.
17 May 1st Air Cavalry Division begins Operation Jeb Stuart III along the border of Quang Tri and Thua Thien Provinces.
18 May Battalions from the 1st Marine Division begin Operation Mameluke
Thrust in the central regions of Quang Nam Province. 20 May Major General Raymond G. Davis replaces Major General Rathvon McC.
Tompkins as Commanding General, 3d Marine Division. 22 May The Marine Corps makes its first use of the North American OV-10A
Bronco as an observation and counter-insurgency aircraft.
26 May Major General Rathvon McC. Tompkins becomes Deputy Commander of III MAF, replacing Major General William J. Van Ryzin.
27 May Peace talks between the United States and North Vietnam break down in
Paris. May Operation Kentucky results in a reported 817 enemy casualties with 134
Marines killed and 611 wounded. May Marine Corps force levels in Vietnam reach 89,000.
1 June Lieutenant General Henry W. Buse, Jr., replaces Lieutenant General Victor H. Krulak as the Commanding General, Fleet Marine Force, Pacific. 5 June Robert F. Kennedy is assassinated.
26 June Major General Carl A. Youngdale relieves Major General Donn J. Robertson as Commander of the 1st Marine Division.
27 June Marine troops begin to dismantle and withdraw from their static defense base at Khe Sanh.
1 July General Creighton Abrams relieves General William Westmoreland as Commander USMACV.
1 July Operation Thor begins in the eastern part of the DMZ. Planes from the Air Force, the Navy, and the Marine Corps, as well as artillery from Army and Marine artillery batteries in the DMZ sector and naval gunfire from cruisers and destroyers off the coast pound enemy artillery installations in the DMZ.
7 July Operation Thor ends. 25 July The 1st Brigade, 5th Infantry Division (Mechanized), USA, arrives in I CTZ and is placed under the operational control of III MAF.