World War II: Allied forces begin the Battle of Keren to capture Keren, Eritrea.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during World War II (1939–1945) to oppose the Axis powers. Its principal members were the "Big Four" – the United Kingdom, United States, Soviet Union, and China.

The Battle of Keren took place from 3 February to 27 March 1941. Keren was attacked by the British during the East African Campaign of the Second World War. A force of Italian regular and colonial troops defended the position against troops mostly from Sudan and British India and Free French forces. The town of Keren, in the colony of Italian East Africa, was of tactical importance to both sides. The road and railway through Keren were the main routes to the colonial capital of Italian Eritrea at Asmara and the Red Sea port of Massawa, which surrendered to the British after the battle.

Keren, historically known as Sanhit, is the second-largest city in Eritrea. It is situated around 91 kilometres (57 mi) northwest of Asmara at an elevation of 1,590 metres (5,220 ft) above sea-level. The city sprawls on a wide basin surrounded by granitic mountains on all sides. It serves as the capital of the Anseba Region, and is home to a number of ethnic groups including the Bilen people and Tigre people.