Until April 1814, Great Britain was at war with Napoleonic France, which limited British war aims in America. During this time the British primarily used a defensive strategy and repelled American invasions of the provinces of Upper and Lower Canada. However, the Americans gained naval control over Lake Erie in 1813, and seized parts of western Ontario. In the Southwest, General Andrew Jackson destroyed the military strength of the Creek nation at the Battle of Horseshoe Bend in 1814.
Although Great Britain was unwilling to draw military forces from the war with France, it still enjoyed a naval superiority on the ocean, and vessels of the North America and West Indies Squadron, based at Bermuda, blockaded American ports on the Atlantic throughout the war, strangling the American economy (initially, the north-eastern ports were spared this blockade as public sentiments in New York and New England were against the war). The Royal Navy and Royal Marines also occupied American coastal islands and landed military forces for raids along the coast, especially around the Chesapeake Bay, encouraging enslaved blacks to defect to the Crown and recruiting them into the Corps of Colonial Marines.
Following the defeat of Napoleon in the spring of 1814, the British adopted a more aggressive strategy, intended to compel the United States to negotiate a peace that restored the pre-war status quo. Thousands of seasoned British soldiers were deployed to British North America. Most went to the Canadas to re-enforce the defenders (the British Army, Canadian militias, and their First Nations allies drove the American invaders back into the United States, but without naval control of the Great Lakes they were unable to receive supplies, resulting in the failure to capture Plattsburgh in the Second Battle of Lake Champlain and the withdrawal from US territory), but a brigade under the command of Major General Robert Ross was sent in early July with several naval vessels to join the forces already operating from Bermuda. The combined forces were to be used for diversionary raids along the Atlantic coast, intended to force the Americans to withdraw forces from Canada. They were under orders not to carry out any extended operations and were restricted to targets on the coast.
An ambitious raid was planned as the result of a letter sent to Bermuda on 2 June by Sir George Prévost, Governor General of The Canadas, who called for a retaliation in response to the "wanton destruction of private property along the north shores of Lake Erie" by American forces under Colonel John Campbell in May 1814, the most notable being the Raid on Port Dover. Prévost argued that,
... in consequence of the late disgraceful conduct of the American troops in the wanton destruction of private property on the north shores of Lake Erie, in order that if the war with the United States continues you may, should you judge it advisable, assist in inflicting that measure of retaliation which shall deter the enemy from a repetition of similar outrages.
The letter was considered by Ross and Vice-Admiral Sir Alexander Cochrane (who had replaced Sir John Borlase Warren earlier that year as the Commander-in-Chief of the North America and West Indies Station of the Royal Navy, headquartered at Admiralty House in Bermuda) in planning how to use their forces. Cochrane's junior, Rear Admiral George Cockburn, had been commanding ships of the squadron in the operations on the Chesapeake Bay since the previous year. On 25 June he wrote to Cochrane stressing that the defenses there were weak, and he felt that several major cities were vulnerable to attack. Cochrane suggested attacking Baltimore, Washington and Philadelphia. On 17 July, Cockburn recommended Washington as the target, because of the comparative ease of attacking the national capital and "the greater political effect likely to result".
On 18 July, Cochrane ordered Cockburn that to "deter the enemy from a repetition of similar outrages ..." You are hereby required and directed to "destroy and lay waste such towns and districts as you may find assailable". Cochrane instructed, "You will spare merely the lives of the unarmed inhabitants of the United States".
In August, the vessels in Bermuda sailed from the Royal Naval Dockyard and St. George's to join those already operating along the American Atlantic coast. After defeating a US Navy gunboat flotilla, a military force totaling 4,370 (composed of British Army, Royal Marines, and Royal Navy detachments for shore service) under Ross was landed in Virginia. After beating off an American force of 1,200 on the 23rd, on the 24th they attacked the prepared defenses of the main American force of roughly 6,400 (US Army soldiers, militiamen, US Marines, and US Navy sailors) in the Battle of Bladensburg. Despite the considerable disadvantage in numbers (standard military logic dictates that a three-to-one advantage is needed in carrying out an attack on prepared defences) and sustaining heavy casualties, the British force routed the American defenders and cleared the path into the capital (President James Madison and the entire government fled the city, and went North, to the town of Brookeville, Maryland). The Burning of Washington took place that night before the force returned to the ships.
The British also sent a fleet up the Potomac to cut off Washington's water access and threaten the prosperous ports of Alexandria, just downstream of Washington, and Georgetown, just upstream. The mere appearance of the fleet cowed American defenders into fleeing from Fort Warburton without firing a shot, and undefended Alexandria surrendered. The British spent several days looting hundreds of tons of merchandise from city merchants, then turned their attention north to Baltimore, where they hoped to strike a powerful blow against the demoralized Americans. Baltimore was a busy port and was thought by the British to harbor many of the privateers who were raiding British shipping. The British planned a combined operation, with Ross launching a land attack at North Point, and Vice-Admiral Sir Alexander Cochrane laying siege to Fort McHenry, which was the point defensive installation in Baltimore Harbor.