The Korean War was a war between North Korea (with the support of China and the Soviet Union) and South Korea (with the support of the United Nations, principally from the United States). The war began on 25 June 1950 when North Korea invaded South Korea following clashes along the border and insurrections in the south. The war ended unofficially on 27 July 1953 in an armistice.

After the surrender of Japan, at the end of World War II, on 15 August 1945, Korea was divided at the 38th parallel into two zones of occupation. The Soviets administered the northern-half and the Americans administered the southern-half. In 1948, as a result of Cold War tensions, the occupation zones became two sovereign states. A socialist state was established in the north under the totalitarian leadership of Kim Il-sung and a capitalist state in the south under the authoritarian leadership of Syngman Rhee. Both governments of the two new Korean states claimed to be the sole legitimate government of all of Korea, and neither accepted the border as permanent.

North Korean Korean People's Army (KPA) forces crossed the border and advanced into South Korea on 25 June 1950. The United Nations Security Council denounced the North Korean move as an invasion, and authorized the formation of the United Nations Command and the dispatch of forces to Korea to repel it. These UN decisions were taken without participation of the Soviet Union and the People's Republic of China, both of which supported North Korea. Twenty-one countries of the United Nations eventually contributed to the UN force, with the United States providing around 90% of the military personnel.

After the first two months of war, South Korean Army (ROKA) and the US forces rapidly dispatched to Korea were on the point of defeat. As a result, the ROKA and US troops retreated to a small area behind a defensive line known as the Pusan Perimeter. In September 1950, an amphibious UN counter-offensive was launched at Incheon, and cut off many KPA troops in South Korea. Those who escaped envelopment and capture were forced back north. UN forces invaded North Korea in October 1950 and moved rapidly towards the Yalu River—the border with China—but on 19 October 1950, Chinese forces of the People's Volunteer Army (PVA) crossed the Yalu and entered the war. The surprise Chinese intervention triggered a retreat of UN forces and Chinese forces were in South Korea by late December.

In these and subsequent battles, Seoul was captured four times, and communist forces were pushed back to positions around the 38th parallel, close to where the war started. After this the front stabilized and the last two years of fighting became a war of attrition. The war in the air, however, was never a stalemate. North Korea was subject to a massive US bombing campaign. Jet fighters confronted each other in air-to-air combat for the first time in history, and Soviet pilots covertly flew in defense of their communist allies.

The fighting ended on 27 July 1953 when the Korean Armistice Agreement was signed. The agreement created the Korean Demilitarized Zone (DMZ) to separate North and South Korea, and allowed the return of prisoners. However, no peace treaty was ever signed, and the two Koreas are technically still at war, engaged in a frozen conflict.[59][60] In April 2018, the leaders of North and South Korea met at the DMZ and agreed to work toward a treaty to formally end the Korean War.

The Korean War was among the most destructive conflicts of the modern era, with approximately 3 million war fatalities and a larger proportional civilian death toll than World War II or the Vietnam War. It incurred the destruction of virtually all of Korea's major cities, thousands of massacres by both sides, including the mass killing of tens of thousands of suspected communists by the South Korean government, and the torture and starvation of prisoners of war by the North Korean command. North Korea became among the most heavily bombed countries in history.

was a campaign of the First World War, fought by the Allies against the German Empire.[a] The battle took place on the Western Front, from July to November 1917, for control of the ridges south and east of the Belgian city of Ypres in West Flanders, as part of a strategy decided by the Allies at conferences in November 1916 and May 1917. Passchendaele lies on the last ridge east of Ypres, 5 mi (8.0 km) from Roulers (now Roeselare) a junction of the Bruges (Brugge) to Kortrijk railway. The station at Roulers was on the main supply route of the German 4th Army. Once Passchendaele Ridge had been captured, the Allied advance was to continue to a line from Thourout (now Torhout) to Couckelaere (Koekelare).

Further operations and a British supporting attack along the Belgian coast from Nieuport (Nieuwpoort), combined with an amphibious landing (Operation Hush), were to have reached Bruges and then the Dutch frontier. Although a general withdrawal had seemed inevitable in early October, the Germans were able to avoid one due to the resistance of the 4th Army, unusually wet weather in August, the beginning of the autumn rains in October and the diversion of British and French resources to Italy. The campaign ended in November, when the Canadian Corps captured Passchendaele, apart from local attacks in December and early in the new year. The Battle of the Lys (Fourth Battle of Ypres) and the Fifth Battle of Ypres of 1918, were fought before the Allies occupied the Belgian coast and reached the Dutch frontier.

A campaign in Flanders was controversial in 1917 and has remained so. The British Prime Minister, David Lloyd George, opposed the offensive, as did General Ferdinand Foch, the Chief of Staff of the French Army. Field Marshal Sir Douglas Haig, commander of the British Expeditionary Force (BEF), did not receive approval for the Flanders operation from the War Cabinet until 25 July. Matters of dispute by the participants, writers and historians since 1917 include the wisdom of pursuing an offensive strategy in the wake of the Nivelle Offensive, rather than waiting for the arrival of the American Expeditionary Force (AEF) in France.

The choice of Flanders, its climate, the selection of General Hubert Gough and the Fifth Army to conduct the offensive, debates over the nature of the opening attack and between advocates of shallow and deeper objectives, remain controversial. The time between the Battle of Messines (7–14 June) and the first Allied attack (the Battle of Pilckem Ridge, 31 July), the extent to which the internal troubles of the French armies influenced the British, the effect of the exceptional weather, the decision to continue the offensive in October and the human costs of the campaign are also debated.