North Korea invades South Korea with 135,000 men, initiating the Korean War.
President Harry S. Truman deploys the 7th Fleet to waters off Taiwan to prevent the spread of the conflict in Korea to other Far East waters.
First air victory of the war. A 68th All-Weather Squadron F-82 shoots down a North Korean Yak fighter. Two more enemy planes are destroyed in this air battle.
Fifth Air Force's 3rd Bombardment Group sends 18 B-26 Invader light bombers against Heijo Airfield near the North Korean capital of Pyongyang: 25 enemy aircraft are destroyed on the ground; one Yak fighter is shot down.
First U.S. infantry unit arrives in Korea: 1st Battalion, 21st Infantry Regiment, 24th Infantry Division. Along with Battery A of the 52nd Field Artillery Battalion, it comprises Task Force Smith.
Off Chumunjin, on Korea's east coast, the USS Juneau helps destroy three of four attacking North Korean torpedo boats.
The Battle of Osan, the first U.S. ground action of the war, begins. Task Force Smith (406 infantrymen and 134 artillerymen) engages and delays advancing North Korean People's Army (NKPA) units.
Fifty-seven Army nurses arrive in Busan, Korea. They help establish a hospital for the wounded. Two days later, on July 8, twelve Army nurses move forward with a mobile Army surgical hospital (MASH) to Taejon.
August 4–September 16
Nearly 85,000 U.S. troops participate in the defense of the Busan Perimeter, including the U.S. Army's 1st Cavalry Division; 2nd, 24th, and 25th Infantry Divisions; and the 1st Provisional Marine Brigade.
U.S. and allied forces land U.S. Marines and U.S. Army troops at Inchon, in an invasion called Operation CHROMITE.
In the Inchon Operation and Liberation of Seoul, U.S. and allies re-capture Seoul on September 27 after a week of fighting.
In the Busan Perimeter breakout, the Eighth U.S. Army (EUSA) breaks out of the Busan Perimeter. Four U.S. divisions (1st Cavalry Division, 2nd, 24th, and 25th Infantry Divisions) participate.
In the war's first airborne operation, 71 C-119s and 40 C-47s of the Far East Air Force's (FEAF) Combat Cargo Command drop 2,860 paratroopers of the 187th Airborne Regimental Combat Team (RCT) at Sukch'on and Sunch'on north of Pyongyang. Only one trooper is killed and 36 are injured in the jump. Paratroopers, in association with ground forces driving north, kill or capture about 6,000 North Koreans during this operation.
Chinese Communist Forces (CCF) launch their first phase offensive of the Korean War.
An F-80 Shooting Star of the 51st Fighter Interceptor Wing shoots down a MiG-15 fighter near Sinuiju. The 30-second dogfight is the first all-jet combat in history.
FEAF B-29s and Navy aircraft attack Yalu River bridges in attempt to isolate the battlefield.
November 25–December 15
Seven U.S. divisions (1st Marine Division, U.S. Army's 1st Cavalry Division, and the 2nd, 3rd, 7th, 24th, and 25th Infantry Divisions) participate in a CCF Counteroffensive in North Korea.
November 27–December 9
The encircled 1st Marine Division fights its way southward from the Chosin Reservoir to the port city of Hungnam in the Battle of the Changjin (Chosin) Reservoir.
Hungnam Operation is complete: the U.S. Navy evacuates 105,000 U.S. and Republic of Korea (ROK) forces.
In the Third Phase CCF Offensive, 500,000 enemy troops push U.N. forces 50 miles south of the 38th Parallel and recapture Seoul.
The 23rd Infantry Regiment (2nd Infantry Division), French Battalion, and 347th Field Artillery Battalion confront several CCF regiments, killing at least 1,300 Chinese in the Battle of the Twin Tunnels.
The Battle of Chipyong-ni is the first mass assault by CCF, 18,000 troops. The CCF offensive is contained by 23rd Regiment (2nd Infantry Division), French Battalion, 1st Ranger Company, 37th Field Artillery Battalion, and Battery B of the 82nd Antiaircraft Artillery Battalion.
February 16, 1951–July 27, 1953
Task Force 95 (U.N. Blockade and Escort Force) blockades Wonsan Harbor. An unprecedented 861-day naval operation, the Siege of Wonsan is the longest effective siege of a port in U.S. Navy history.
March 7–April 4
Operation RIPPER drives the Communists back to the 38th Parallel and retakes Seoul. Seven U.S. divisions participate (U.S. Army's 1st Cavalry Division; 2nd, 3rd, 7th, 24th, and 25th Infantry Divisions; and the 1st Marine Division).
One hundred twenty C-119s and C-46s drop 3,437 paratroopers of the 187th Regimental Combat Team near Munsan-ni in Operation TOMAHAWK, the second largest airborne operation of the war.
In the war's first major aerial duel, more than 40 MiG-15s attack a B-29 formation, shooting down two bombers. Eleven of the MiGs are destroyed, seven by B-29 gunners.
The largest single battle of the Korean War is the CCF First Spring Offensive. CCF launch the offensive with 250,000 men in 27 divisions. Five U.S. Army divisions (2nd, 3rd, 7th, 24th, and 25th) participate.
Four U.S. divisions (U.S. Army's 2nd, 3rd, and 25th Infantry Divisions, and the 1st Marine Division) participate in the CCF Second Spring Offensive.
May 20–September 20
Operation STRANGLE, a massive, all-out air interdiction campaign 20 is carried out by FEAF, TF 77, and the 1st Marine Aircraft Wing (MAW).
The 1st Marine Division encounters heavy North Korean resistance, but succeeds in taking its objective in the Battle for the Punchbowl (vicinity Hwach'on Reservoir).
August 18–September 5
In the Battle of Bloody Ridge (Hill 983), the 15th Field Artillery Battalion sets a record by firing 14,425 rounds in 24 hours.
September 13–October 15
The 2nd Infantry Division seizes Heartbreak Ridge in the Battle of Heartbreak Ridge (Hill 931).
A company of 228 Marines is lifted by 12 Sikorsky S-55s in Operation SUMMIT, the first helicopter deployment of a combat unit.
In a rare air battle with Communist bombers, 31 Sabres knock down eight Tu-2 bombers, three La-9 propeller-driven fighters, and one MiG-15.
Korean War truce talks began July 10, 1951. Although the talks started slowly, on November 27, 1951, the two sides agree on the 38th Parallel as the line of demarcation and military operations slow down almost immediately. When Gen. Mark Clark assumes command of U.N. forces in Korea on May 12, 1952, he is confronted with a military deadlock on the front lines, stalled Armistice negotiations, and a violent prisoner of war situation on the island of Koje-do, off the southern coast of South Korea. Clark believes that the Communists only understood force and stepped up military pressure on the enemy to break the stalemate at Panmunjom.
Raid on Agok. Nine tanks of the 245th Tank Battalion, 45th Infantry Division, retaliate for three raids on the division's sector.
The 45th Infantry Division launches a two-phased series of attacks called Operation COUNTER to establish 11 patrol bases in the Old Baldy area. Second and 3rd Battalions, 180th Infantry Regiment, fight fiercely for Outpost Eerie on Hill 191, which is counterattacked by two Chinese battalions.
The Battle for Old Baldy (Hill 266) begins; the engagements last until August 4.
FEAF and Navy planes launch massive air strikes against North Korea's hydroelectric power grid, causing an almost complete blackout for more than two weeks. Results of strikes extend into northeast China, which loses nearly 25 percent of its electrical requirements.
August 12-16–September 5-15
The first major Marine ground action in western Korea, the Battle of Bunker Hill (Hill 122), is fought by the 1st Marine Division.
FEAF and carrier planes bomb Pyongyang in a 1,403-sortie assault—the largest single-day raid of the war.
A total of 144 planes from three carriers destroy the oil refinery at Aoji, North Korea, in the largest all-Navy raid.
At Outpost Kelly, the 65th Infantry Regiment (3rd Infantry Division) is besieged by CCF.
October 9- July 1953
"Cherokee" strikes and the 7th Fleet bombing campaign against battlefront enemy supply facilities begins.
In Operation SHOWDOWN/Battle of Hill 598 (Sniper Ridge), the 7th Infantry Division battles the Chinese near Kumhwa, the right leg of the Iron Triangle.
The Battle of the Hook takes place.
Hill 851, the Heartbreak Ridge area, is held by the 2nd Battalion, 160th Infantry Regiment (40th Infantry Division).
At T-Bone Hill, the 38th Infantry Regiment (2nd Infantry Division) repels Chinese forces during an intense battle.
Operation SMACK is an assault on Spud Hill by elements of the 31st Infantry Regiment (7th Infantry Division).
Hill 355 (Little Gibraltar), held by the 9th Infantry Regiment (2nd Infantry Division), is assaulted by Chinese.
The Old Baldy/Pork Chop Complex is held by 31st Infantry Regiment (7th Infantry Division). The 32nd Regiment (7th Infantry Division) relieves the 31st.
Outposts at the Nevada cities (Las Vegas, Reno, Carson), held by the 5th Marine Regiment, come under heavy attack. A Chinese regiment is destroyed.
The 17th and 31st Infantry Regiments (7th Infantry Division) are hit hard and suffer heavy casualties in the Battle of Pork Chop Hill.
Operation Little Switch exchanges sick and wounded POWs, including 149 Americans.
The raid on Toksan Dam, a dramatic strike by 58th Fighter-Bomber Wing F-84s, destroys a major irrigation system. Five miles of valuable rice crops are scoured and miles of highways and railroad tracks are destroyed. Further attacks on irrigation dams follow over the next two weeks.
The USS Princeton launches 184 sorties, establishing a single-day Korean War record for offensive sorties flown from a carrier.
Navy and Marine Corps aircraft fly 910 sorties—the highest combined number for a single day.
FEAF Sabres destroy 16 MiGs, the largest number shot down in one day.
The 7th Infantry Division is ordered to evacuate its defensive positions after five days of fighting in the Battle of Pork Chop Hill.
The Battle of Kumsong River Salient is the last Communist offensive. CCF launches a six-division attack partly directed at the U.S. IX Corps (3rd, 40th, and 45th Infantry Divisions). The 187th RCT is attached to the 2nd Infantry Division during the fighting.
In the final U.S. ground combat, heavy enemy (3,000 men) attack is launched in the Berlin Complex ("Boulder City") area held by the 7th and 1st Marine Regiments. The last Marine ground actions of the war are fought on Hills 111 and 119.
F-86 pilot downs an enemy transport near the Manchurian border in the last air kill of the war.
The United States, North Korea, and China sign an armistice, which ends the war but fails to bring about a permanent peace. To date, the Republic of Korea (South) and Democratic Peoples' Republic of Korea (North) have not signed a peace treaty. A total of 33,651 service members die in battle during the Korean War: 27,709 U.S. Army; 4,269 U.S. Marines; 1,198 U.S. Air Force; and 475 U.S. Navy. Over 7,100 service members become prisoners of war.