The Philadelphia campaign (1777–1778) was a British effort in the American Revolutionary War to gain control of Philadelphia, the Revolutionary-era capital where the Second Continental Congress convened and signed the Declaration of Independence, which formalized and escalated the war.
As part of the Philadelphia campaign, British General William Howe, after failing to draw the Continental Army under General George Washington into a battle in North Jersey, embarked his army on transports, and landed them at the northern end of the Chesapeake Bay. From there, he advanced northward toward Philadelphia. Washington prepared defenses against Howe's movements at Brandywine Creek, but was flanked and beaten back in the Battle of Brandywine on September 11, 1777. After further skirmishes and maneuvers, Howe entered and occupied Philadelphia. Washington then unsuccessfully attacked one of Howe's garrisons at Germantown before retreating to Valley Forge for the winter.
Howe's campaign was controversial because, while he succeeded in capturing the American capital of Philadelphia, he proceeded slowly and did not aid the concurrent campaign of John Burgoyne further north, which ended in disaster for the British in the Battles of Saratoga and brought France into the war. Howe resigned during the occupation of Philadelphia and was replaced by his second-in-command, General Sir Henry Clinton. Clinton evacuated Philadelphia and moved his troops back to New York City in 1778, in order to stiffen that city's defenses against a possible combined Franco-American attack. Washington then harried the British Army all the way across New Jersey, and forced a battle at Monmouth Court House that was one of the war's largest battles.
At the end of the Philadelphia campaign in 1778, the two armies found themselves in roughly the same strategic positions that they had been in before Howe launched the attack on Philadelphia.
History
British plan to capture Philadelphia
Following Howe's capture of New York City and Washington's success in the Battles of Trenton and Princeton, the two armies settled into an uneasy stalemate in the winter months of early 1777. While punctuated by numerous skirmishes, the British Army continued to occupy outposts at New Brunswick and Perth Amboy in New Jersey.
In 1777, Howe proposed to George Germain, the British civilian official responsible for war's conduct, that British expedition be launched with the goal of capturing Philadelphia, the seat of the rebellious Second Continental Congress. Germain approved Howe's plan, although with fewer troops than Howe requested. He also approved plans by John Burgoyne for an expedition to "force his way to Albany" from Montreal. Germain's approval of Howe's expedition included the expectation that Howe would be able to assist Burgoyne, effecting a junction at Albany between the forces of Burgoyne and troops that Howe would send north from New York City.
Howe decided in early April 1777 against taking the British Army over land to Philadelphia through New Jersey since this route would entail having to cross of the broad Delaware River under hostile conditions and likely require the transportation or construction of necessary watercraft. Howe's plan, sent to Germain on April 2, isolated Burgoyne from any possibility of significant support, since Howe instead would take the British Army to Philadelphia by sea, and the New York garrison would be too small for any significant offensive operations up the Hudson River to assist Burgoyne.