The British Army are the ground forces of the United Kingdom's military, and formerly those of Great Britain. Its modern form was founded in 1660 as the "English Army", but in 1707 it merged with the Scottish Army to form the British Army, representing the new union of England and Scotland. In 2016, the British Army had a strength of 87,610 troops, and it had a reputation as one of the strongest militaries in the world. The British Army has seen action on almost every continent, whether it was expanding Britain's colonial empire or defending British interests abroad.
The British Army was founded in 1660 as the "English Army", but in 1707 England and Scotland merged to form Great Britain, and their armies merged into the new British Army. Its founding year was during the War of the Spanish Succession, and the British army first fought in that war, against France and Spain. They allied with Austria and were led by the inspirational John Churchill (Duke of Marlborough). The British went on to prove their skills in the War of the Austrian Succession, again against France, in the 1740s, by which point they had adopted new military doctrines and had also incorporated the Grenadiers unit into their army.
In 1756-1763, the British Army dominated France during the Seven Years' War; it was able to secure more lands for their Thirteen Colonies in the Americas as well as large parts of India. From 1763 to 1918, Britain rapidly expanded its empire with its experienced army and its invincible Royal Navy. The British were usually the victors in conventional warfare, but they were defeated by the rebel United States (former Thirteen Colonies) during the American Revolutionary War of 1775-1783. Despite this loss, the British continued to perform well against other countries and were the cause of the downfall of the Napoleonic Empire during the Napoleonic Wars (1796-1815). The British liberated all of Spain and Portugal from the French army from 1808 to 1814 alongside Spanish guerrillas and also defeated Napoleon in the decisive Battle of Waterloo on 18 June 1815. At the same time, they fought the United States to a draw during the War of 1812.
After the Napoleonic Wars, the British Army grew stronger as it adopted much more technology that was researched during the Industrial Revolution era (which started in Britain, who had the advantage of clustered resources as well as being an island, meaning that it had a large trade navy). Britain's use of rifles was the downfall of many African empires that they conquered from the 1830s to 1890s, and they won the Crimean War against the Russian Empire in 1853 to 1856 alongside France and Sardinia. Britain's army was crucial in the conquest of the Republic of Queimada in 1854, crushing a slave revolt on the island before occupying it. Britain's armies continued to expand until the late 1800s and early 1900s, when they were nearly defeated by Boer settlers in South Africa in the Second Boer War of 1899-1902 (they lost the minor First Boer War in 1882) and were massacred by African tribes such as the Ashanti and the Mahdists.
In 1914, Britain entered World War I on the side of France after the German Empire invaded neutral Belgium in the process of attacking France. Britain's army was made up of conscript reservists (men with previous military training kept in reserve for later use), and many were not used to bloody trench warfare and Germany's use of poison gas. It was only in 1916, when Herbert Kitchener patented the New Army (also called "Kitchener's Mob"), did Britain make a comeback. They eventually began counterattacking against Germany and in 1917 adopted tanks, and in 1918 Britain, France, and the United States teamed up and drove the Germans back into Belgium and clean out of France. Their victory was complete, and the British Army was strong once more.
In the aftermath of World War I the British adopted chemical gas and used it to crush Kurdish and Shi'a revolts in the Middle East in the 1920s, and they spent the 1920s-30s modernizing their army. They created the Royal Air Force (RAF) to support the British Army, who also gained support from "paratroopers" (troops who jumped out of planes with parachutes).
In 1939, Britain entered World War II, this time to support France's ally of Poland, who was under attack from Nazi Germany. Britain had previously allowed Germany to expand its borders to include Czechoslovakia and formerly-occupied regions of the country, and allowed dictator Adolf Hitler to regain power and build up Germany's Wehrmacht army. Britain's British Expeditionary Force (BEF) was defeated in the campaign in Belgium and France, defeated by Germany's lightning offensive of tanks, planes, and men. However, when Winston Churchill became Prime Minister in 1940, he mustered up the strength of Britain and declared that they would fight to the last man. Under his tenure, Britain's air force repelled the German air invasion of Britain and his armies defeated the Italians and Germans in North Africa from 1941-1943 under Bernard Montgomery (despite many losses to Erwin Rommel).
In 1944, Britain's army invaded German-occupied France alongside the United States, Free French, Polish, and Canadian units, landing at Gold, Juno, and Sword beaches in Normandy. They fought intense battles such as the Battle of Caen and the Battle of Villiers Bocage, but they succeeded in liberating Paris on 30 August. For the rest of 1944 they pushed into Belgium and captured Antwerp before moving into the Netherlands. Britain's army then carried out the invasion of Germany itself in 1945, and ended the war meeting up with allied Soviet Union forces from the other side of Europe on the banks of the Elbe River at Torgau on 25 April 1945, along with Americans (on the same side of the river as the British).
During the Cold War that immediately followed World War II, Britain fought in the Korean War as well as in the wars in Africa against rebels, but the British did not fight as much as the United States did against communist nations. However, they continued to modernize despite the lack of war and proved their fighting capabilities in the Gulf War of 1990-91 against Iraq. Britain again fought in the Afghanistan War of 2001-2014 and was America's biggest ally during the Iraq War and occupation of 2003-2011.