The Salt March, also known as the Salt Satyagraha, Dandi March and the Dandi Satyagraha, was an act of nonviolent civil disobedience in colonial India led by Mahatma Gandhi. The twenty-four day march lasted from 12 March 1930 to 6 April 1930 as a direct action campaign of tax resistance and nonviolent protest against the British salt monopoly. Another reason for this march was that the Civil Disobedience Movement needed a strong inauguration that would inspire more people to follow Gandhi's example. Gandhi started this march with 78 of his trusted volunteers. The march spanned 239 miles (385 km), from Sabarmati Ashram to Dandi, which was called Navsari at that time (now in the state of Gujarat). Growing numbers of Indians joined them along the way. When Gandhi broke the British Raj salt laws at 8:30 am on 6 April 1930, it sparked large scale acts of civil disobedience against the salt laws by millions of Indians.After making the salt by evaporation at Dandi, Gandhi continued southward along the coast, making salt and addressing meetings on the way. The Congress Party planned to stage a satyagraha at the Dharasana Salt Works, 25 mi (40 km) south of Dandi. However, Gandhi was arrested on the midnight of 45 May 1930, just days before the planned action at Dharasana. The Dandi March and the ensuing Dharasana Satyagraha drew worldwide attention to the Indian independence movement through extensive newspaper and newsreel coverage. The satyagraha against the salt tax continued for almost a year, ending with Gandhi's release from jail and negotiations with Viceroy Lord Irwin at the Second Round Table Conference. Although over 60,000 Indians were jailed as a result of the Salt Satyagraha, the British did not make immediate major concessions.The Salt Satyagraha campaign was based upon Gandhi's principles of non-violent protest called satyagraha, which he loosely translated as "truth-force". Literally, it is formed from the Sanskrit words satya, "truth", and agraha, "insistence". In early 1920 the Indian National Congress chose satyagraha as their main tactic for winning Indian sovereignty and self-rule from British rule and appointed Gandhi to organise the campaign. Gandhi chose the 1882 British Salt Act as the first target of satyagraha. The Salt March to Dandi, and the beating by the colonial police of hundreds of nonviolent protesters in Dharasana, which received worldwide news coverage, demonstrated the effective use of civil disobedience as a technique for fighting social and political injustice. The satyagraha teachings of Gandhi and the March to Dandi had a significant influence on American activists Martin Luther King Jr., James Bevel, and others during the Civil Rights Movement for civil rights for African Americans and other minority groups in the 1960s. The march was the most significant organised challenge to British authority since the Non-cooperation movement of 192022, and directly followed the Purna Swaraj declaration of sovereignty and self-rule by the Indian National Congress on 26 January 1930. It gained worldwide attention which gave impetus to the Indian independence movement and started the nationwide Civil Disobedience movement which continued until 1934.

The British Empire was composed of the dominions, colonies, protectorates, mandates, and other territories ruled or administered by the United Kingdom and its predecessor states. It began with the overseas possessions and trading posts established by England between the late 16th and early 18th centuries.

At its height it was the largest empire in history and, for over a century, was the foremost global power. By 1913 the British Empire held sway over 412 million people, 23 per cent of the world population at the time, and by 1920 it covered 35,500,000 km2 (13,700,000 sq mi), 24 per cent of the Earth's total land area. As a result, its constitutional, legal, linguistic, and cultural legacy is widespread. At the peak of its power, it was described as "the empire on which the sun never sets", as the sun was always shining on at least one of its territories.During the Age of Discovery in the 15th and 16th centuries, Portugal and Spain pioneered European exploration of the globe, and in the process established large overseas empires. Envious of the great wealth these empires generated, England, France, and the Netherlands began to establish colonies and trade networks of their own in the Americas and Asia. A series of wars in the 17th and 18th centuries with the Netherlands and France left England (Britain, following the 1707 Act of Union with Scotland) the dominant colonial power in North America. Britain became the dominant power in the Indian subcontinent after the East India Company's conquest of Mughal Bengal at the Battle of Plassey in 1757.

The American War of Independence resulted in Britain losing some of its oldest and most populous colonies in North America by 1783. British attention then turned towards Asia, Africa, and the Pacific. After the defeat of France in the Napoleonic Wars (1803–1815), Britain emerged as the principal naval and imperial power of the 19th century and expanded its imperial holdings. The period of relative peace (1815–1914) during which the British Empire became the global hegemon was later described as "Pax Britannica" ("British Peace"). Alongside the formal control that Britain exerted over its colonies, its dominance of much of world trade meant that it effectively controlled the economies of many regions, such as Asia and Latin America. Increasing degrees of autonomy were granted to its white settler colonies, some of which were reclassified as dominions.

By the start of the 20th century, Germany and the United States had begun to challenge Britain's economic lead. Military and economic tensions between Britain and Germany were major causes of the First World War, during which Britain relied heavily on its empire. The conflict placed enormous strain on its military, financial, and manpower resources. Although the empire achieved its largest territorial extent immediately after World War I, Britain was no longer the world's preeminent industrial or military power. In the Second World War, Britain's colonies in East Asia and Southeast Asia were occupied by the Empire of Japan. Despite the final victory of Britain and its allies, the damage to British prestige helped accelerate the decline of the empire. India, Britain's most valuable and populous possession, achieved independence as part of a larger decolonisation movement, in which Britain granted independence to most territories of the empire. The Suez Crisis of 1956 confirmed Britain's decline as a global power, and the transfer of Hong Kong to China on 1 July 1997 marked for many the end of the British Empire. Fourteen overseas territories remain under British sovereignty. After independence, many former British colonies joined the Commonwealth of Nations, a free association of independent states. Fifteen of these, including the United Kingdom, retain a common monarch, currently Queen Elizabeth II.