The British Empire was the largest colonial empire established. Among its foremost colonies/territories were those of India, Canada and Australia. These were a few of the more notable victories and defeats for Britain's empire.
Battle of Trafalgar
In 1805, Britain was at war with Napoleon and France. The French armies had defeated many others in Europe, but they could not defeat the British unless they beat the Royal Navy first. To match the Royal Navy, a combined French and Spanish armada to defeat a Royal Navy fleet off cape Trafalgar, Spain.
Despite having a smaller number of ships at their disposal, Nelson inspired them to a crushing victory at the Battle of Trafalger. With a majority of the Spanish and French ships wiped out, it ensured that the Royal Navy retained a dominant naval presence in British waters. As such, France could not invade and defeat Britain.
Trafalgar was one of the most famous victories for the British Empire. The battle ensured that the Royal Navy remained the world's dominant navy for much of the 19th century. Had Britain lost this battle, then the empire may well have been shattered.
Battle of Amiens
From 1914 the British Empire had been at war with the expanding German Empire. Britain had their victories and defeats such as the Gallipoli Campaign. The German U – boat Campaign in 1917 had some impact, but as Britain reduced merchant shipping losses with their convoys they were not about to wave the white flag.
However, with additional reinforcements Germany renewed their advance in France in 1918. The advances pushed the British and French back to River Marne. Once again it seemed that the German army could triumph in France and bring victory to the German Empire in WW1. Only when France halted the German advance at the Second Battle of the Marne did Britain and their allies advance.
The most notable battle in 1918 was probably the Battle of Amiens. In this battle, Britain was influential as their officers effectively combined tanks, aircraft and infantry. The Germans at Amiens surrendered in number, and their army never recovered from the defeat. Thus, the victory at the Amiens was perhaps the first that highlighted the Germans could not win the war. With German lines collapsing in France, the war ended with the November 11 armistice.
Amiens was the battle that ensured a victory for Britain in WW1. The postwar treaties ensured the empire's expansion with additional territories as the German and Turkish empires dissolved. Their triumphs in the war with Ottoman Turkey left the British dominant in the Middle East. With new territories the empire reached its greatest extent in 1919.
Fall of Singapore
The most notable British battle in the 1940s was perhaps the Battle of Singapore, which was a defeat. Then a smaller Japanese army overran the British and Commonwealth divisions in Singapore in 1942. As the Japanese Empire in the Pacific expanded, Britain's empire crumbled.
Singapore was later returned to Britain after the defeat of the Japanese Empire. However, the loss of Singapore at the Battle of Singapore highlighted that Britain's military could not effectively defend the whole of the empire. The decline of the empire began there.
General Election (1945)
Britain might have emerged victorious in their war with the Axis, but that was not enough to preserve the empire. That much was guaranteed when Labour won the 1945 general election. One of their policies was decolonization. As such, it was clear that Britain would begin to abandon its colonies in the postwar period.
India Leaves the British Empire
To avert a potential Civil War, Britain hastened India's departure from the empire. Consequently, India effectively left the British Empire in 1947. Even though Britain still retained much of the empire in 1947, the loss of this formerly vital colony began the period of decolonization. Gradually, colonies across the world left the British Empire.