He spent most of his years in the colonial administration of British North America working to defeat New France, but his lack of formal military training led to political difficulties and his eventual downfall.

Politically well connected, Shirley began his career in Massachusetts as advocate general in the admiralty court, and quickly became an opponent of Governor Jonathan Belcher.

"[1] His difficulties in organizing expeditions in 1755 and 1756 were compounded by political disputes with New York politicians, and over military matters with Indian agent Sir William Johnson.

[5] His family was connected by marriage to the Duke of Newcastle, who became an important patron and sponsor of Shirley's advancement, and to that of Arthur Onslow, the Speaker of the House of Commons.

[9] Shirley also made common cause with Samuel Waldo, a wealthy merchant and major landowner in the province eastern district (present-day Maine) where Belcher's lax enforcement of timber-cutting laws was harming his business with the Royal Navy.

[17] The exact reasons for Belcher's dismissal have been a recurring subject of scholarly interest, due to the many colonial, imperial, and political factors at play.

[18] Two principal themes within these analyses are Belcher's acquisition of many local enemies, and the idea that good imperial governance in London eventually required his replacement.

"[20] Historian Stephen Foster further notes that someone as powerful as Newcastle was at the time generally had much weightier issues to deal with than arbitrating colonial politics.

In this instance, however, imperial and colonial considerations coincided over the need for Massachusetts to provide a significant number of troops for Newcastle's proposed West Indies expedition in the War of Jenkins' Ear.

Shirley had, prior to its capture, received a request for assistance from the lieutenant governor of Nova Scotia, Paul Mascarene, for support in the defence of Annapolis Royal.

[40] Shirley and other leaders in New England and New York sent letters to colonial authorities in London seeking support for such an expedition, citing the vulnerable conditions at Louisbourg.

[47] More than 4,000 men on more than 90 transports (mainly fishing boats and coastal traders), escorted by six colonial guard ships, descended on Canso, where the expedition waited for the ice to clear from Gabarus Bay, the site just south of Louisbourg that had been chosen for the troop landing.

After capturing the French fort he wrote to Newcastle, proposing a series of expeditions to gain control of all of North America as far west as the Mississippi River, starting with one that would go up the Saint Lawrence from Louisbourg.

[63] In May 1746 he received plans for London outlining an attempt on Quebec using Royal Navy and provincial forces, while a second expedition was to attack Fort Saint-Frédéric on Lake Champlain.

[66] While waiting for definite word from London of plans for 1747 Shirley beefed up the province's western defenses, and in the spring of 1747 he began sending supplies to the Hudson River valley in anticipation of a move toward Fort Saint-Frédéric.

In 1702 Fort William on Castle Island had fired on a Royal Navy ship as it tried to leave Boston Harbour with six recently impressed men aboard.

[75] Two years later Commodore Charles Knowles, who served as Governor of Louisbourg after its capture, had a large number of seamen from Boston harbour impressed for service in his squadron.

Some, such as Samuel Adams (father of the famous American Revolution leader), advocated placing the money in London banks to serve as backing for the paper currency issued by the colonies.

[82] In the meantime, Governor Shirley had been trying to finance a campaign to capture Fort St. Frédéric (at present-day Crown Point, New York), for which he issued more paper money.

[84] Samuel Adams edited and Gamaliel Rogers and Daniel Fowle published The Independent Advertiser, which regularly criticised the British government and Shirley's administration.

[85] William Douglass, a prominent physician in Boston, wrote a series of pamphlets (published by Rogers and Fowle) attacking Shirley, Commodore Knowles, and the whole conduct of the campaign for Louisbourg and its occupation.

[88] While Shirley was abroad, Hutchinson, Andrew Oliver, and others served as his surrogates,[89] and he carefully instructed Lieutenant Governor Spencer Phips to not give his enemies opportunities to manoeuvre in his absence.

[92] Newcastle may have been upset with Shirley, who had accepted an unexpected offer from Bedford to participate in a commission established to delineate the boundaries between the British and French territories in North America.

When (false) rumors reached Boston in 1754 of French military activity on the province's northern frontier (Maine), Shirley was quick to organize an expedition to the Kennebec River to bolster the area's defenses.

[104] Shirley was approached by Nova Scotia Governor Charles Lawrence for assistance in dealing with the French threat on that province's frontiers, suggesting that they collaborate on military actions there.

Braddock declared that Duquesne would be his target, but he authorized Shirley to take his regiment and that of Sir William Pepperrell to Fort Niagara, and confirmed Johnson's command of the Lake George campaign.

[123] Rumors of French movements brought a flurry of activity in November, but when the opposition failed to materialize, much of Johnson's force abandoned the camp to return home.

Johnson, who was being advised by Thomas Pownall, continued to assert his exclusive authority over interactions with Indians, and renewed complaints about Shirley's interference in recruiting for the 1755 campaign.

[130] As commander-in-chief, Shirley made a grandiose proposal for the 1756 campaign season in November 1755, continuing the routes of attack begun in 1755 and adding an expedition to Quebec via the Kennebec River.

Military affairs continued to deteriorate on the New York frontier before Loudoun finally arrived in July 1756;[135] Fort Oswego fell to the French on 10 August.