The British Empire comprises the dominions, colonies, protectorates, mandates, and other territories ruled or administered by the United Kingdom, that had originated with the overseas colonies and trading posts established by England in the late 16th and early 17th centuries. In the late 19th century, British power was challenged by both Germany and the United States. Subsequently, these opposing powers led to the greater diminishing of the British Empire after the Kaiser's War and the Great War.
The British Empire's foundation arose from series of wars in the 17th and 18th centuries with the Netherlands and France left Britain the dominant colonial power in North America and India. Despite the loss of the United States in North America in 1783, British attention soon turned towards Africa, Asia and the Pacific. Following the defeat of Napoleonic France in 1815, Britain enjoyed a century of effectively unchallenged dominance, and expanded its imperial holdings across the globe.
When the Kaiser's War began in 1916, Britain entered the conflict on the side of the Entente in response to unrestricted submarine warfare. British and French forces, however, were unable to prevent the Germans from overwhelming France. By 1920, the Entente was forced into a white peace with Germany in response to civil unrest in their nations and against communist threats from the Soviet Union. In spite of Germany becoming the unofficial hegemony of central Europe, Britain still retain its overseas territories. But the military losses to the Allies in the war fueled disenchanted Entente veterans to feel that their sacrifices were for nothing and leading to the rise of croixism to counter Soviet communism and American capitalism.
Contention resume in Europe when the British Empire along with France placed a naval blockade on Germany in response to German retaliation to civil unrest in the former Austro-Hungarian Empire; however, the blockade allowed the Entente navy to indiscriminately target any ships bounded for Germany. Ultimately, Britain declared war on Germany and initiating the Great War. The United States also declared war on the Entente in response to the losses of inbound American ships for Germany to the blockade - although this gave the Americans an excuse to expand its borders. The British Empire suffered the loss of Canada to the Americans before the declaration of war could reached the British embassy. War against Germany turned against the British as German forces invaded France by 1944. In the same year, Belfast was destroyed by an American nuclear bomb. Britain and its allies were forced into surrender and its empire was carved up by the victors. The British Empire was no more.
By the 23rd century, the remnants of the British Empire was reconstituted into a republican government and strongly under American influence. It is during this period that British dissidents and nationalists were exiled off planet.
In the aftermath of the Collapse, surviving British remnants established planetary states that proclaimed themselves as continuations of the British Empire. On Neu Stuttgart IV, British nationalists established the so-called "Restored British Empire". Pre-Collapse republican British founded the Kingdom of South Anglia.