On the outbreak of the American war, he was appointed to a command, and arrived in Boston in May 1775.... In 1776, he was at the head of the British reinforcements that sailed up the Saint Lawrence River and relieved Quebec City, which was under siege by the Continental Army. He led forces under General Guy Carleton in the drive that chased the Continental Army from the province of Quebec. Carleton then led the British forces onto Lake Champlain, but was, in Burgoyne's opinion, insufficiently bold when he failed to attempt the capture of Fort Ticonderoga after winning the naval Battle of Valcour Island in October.
Burgoyne, seeking to command a major force, proposed to isolate New England by an invasion from Quebec into New York. This had already been attempted by General Carleton in 1776, although he had stopped short of a full-scale invasion due to the lateness of the season. Carleton was heavily criticized in London for not taking advantage of the American retreat from Quebec, and he was also intensely disliked by Germain. This, combined with rival Henry Clinton's failed attempt to capture Charleston, South Carolina, placed Burgoyne in a good position to get command of the 1777 northern campaign.
Burgoyne presented a written plan to Lord Germain on February 28, 1777; Germain approved it and gave Burgoyne command of the main expedition.
Burgoyne's invasion plan from Quebec had two components: he would lead the main force of about 8,000 men south from Montreal along Lake Champlain and the Hudson River Valley while a second column of about 2,000 men (which Barry St. Leger was chosen to lead), would move from Lake Ontario east down the Mohawk River valley in a strategic diversion. Both expeditions would converge upon Albany, where they would link up with troops from Howe's army marching up the Hudson. Control of the Lake Champlain-Lake George-Hudson River route from Canada to New York City would cut off New England from the rest of the American colonies.
The last part of Burgoyne's proposal, the advance by Howe up the Hudson from New York City, proved to be the most controversial part of the campaign. Germain approved Burgoyne's plan after having received Howe's letter detailing his proposed offensive against Philadelphia. Whether Germain told Burgoyne, who was still in London at that time, about Howe's revised plans is unclear: while some sources claim he did, others state that Burgoyne was not notified of the changes until the campaign was well underway. Historian Robert Ketchum believes that Burgoyne would probably have been aware of the problems that lay ahead had he been notified of the Philadelphia plan.
Whether Germain, Howe, and Burgoyne had the same expectations about the degree to which Howe was supposed to support the invasion from Quebec is also unclear. What is clear is that Germain either left his generals with too much latitude, or without a clearly defined overall strategy. In March 1777 Germain had approved of Howe's Philadelphia expedition and did not include any express orders for Howe to go to Albany. Yet Germain also sent Howe a copy of his instructions to Carleton which plainly stated that the northern army was to make a junction with Howe's army at Albany. In a letter from Germain to Howe dated May 18, 1777 he made clear that the Philadelphia expedition should:
be executed in time for you to co-operate with the army ordered to proceed from Canada and put itself under your command.
This last letter, however, was not received by Howe until after he had departed New York for the Chesapeake. To attack Philadelphia Howe could either have moved overland through New Jersey or by sea via the Delaware Bay, both options would have kept him a position to aid Burgoyne if necessary. The final route he took, through the Chesapeake Bay, was immensely time-consuming and left him wholly unable to assist Burgoyne as Germain had envisioned. The decision was so difficult to understand that Howe's more hostile critics accused him of deliberate treachery.
Burgoyne returned to Quebec on May 6, 1777, bearing a letter from Lord Germain which introduced the plan but lacked some details. This produced another of the conflicts of command that plagued the British throughout the war. Lieutenant General Burgoyne technically outranked Major General Carleton, but Carleton was still the governor of Quebec. Germain's instructions to Burgoyne and Carleton had specifically limited Carleton's role to operations in Quebec. This slight against Carleton, combined with Carleton's failure to get command of the expedition, led to his resignation later in 1777, and to his refusal to supply troops from the Quebec regiments to garrison the forts at Crown Point and Ticonderoga after they were captured.