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Britain's loss of America in the War of Independence (1775-1783) is typically attributed to the failings of its key political and military decision makers who were, in Andrew O'Shaughnessy's words, "associated with opposition to progress and with attempting to introduce an authoritarian style of government". They have, he writes, become cartoon figures of incompetence and mediocrity in a story with an inevitable ending, "as history progresses towards modernity".

Quite rightly, O'Shaughnessy gives the quality of the opposition its due. He notes the change of opinion by British general James Grant, who in 1775 thought the rebels too cowardly to fight, but four years later conceded that he "never saw better troops than some of the rebel regiments". None was more capable a commander than George Washington: shrewd in his choice of advisers, he "understood the politics of warfare" and "kept his army intact and out of reach of the British". All true, but it is only fair to add that Washington made his fair share of errors – notably his eagerness to beat the British at their own game by offering pitched battle – that might have been fatal to the rebel cause.

One weakness of O'Shaughnessy's multi-biographical approach is that it necessarily involves repetition as the same campaign is told from a different perspective; but this is also a strength as we learn, for example, that the fatal surrender at Yorktown was more down to Admiral Sir George Rodney's refusal to reinforce the British fleet off Virginia because he was keen to protect the prize money he had won at St Eustatius, than it was to Cornwallis's irresponsible adventurism.

In offering a warts and all approach to his biographical subjects, O'Shaughnessy does not entirely dispel the view that some of Britain's war leaders were either myopic or incompetent. He concedes that George III's hardline response to the pre-war unrest in America "gave the colonies the impression that it was he who had rejected them rather than the other way round", and that the monarch was "crucially influential in prolonging the war, which became a personal crusade". He quotes another commander describing Cornwallis's actions at the defeat at Trenton in 1776 as "the most consummate ignorance ever heard of [in] any officer above a corporal"; and he accepts that General Burgoyne contributed to his downfall at Saratoga in 1777 by overconfidence.

But overall he has drawn a series of excellent and finely nuanced portraits of Britain's war leaders that puts their actions, and the war as a whole, into a much-needed broader context. Many were indeed highly talented and forward-thinking politicians, administrators and commanders who, for the most part, did reasonably well in a near-hopeless situation. The opposition politician Charles James Fox said as much when he concluded that the generals had not failed for want of professional skill, bravery or devotion to duty, "but merely from being employed on a service in which it was impossible to succeed".

That was not entirely true, as O'Shaughnessy himself concedes; but the proof of the first part of Fox's assertion lies in the fact that many of the commanders – notably Admirals Howe and Rodney, and General Cornwallis – went on to have highly successful careers and became "the men who saved Canada, India, Gibraltar and the British Caribbean", thus laying the foundations for Britain's huge imperial expansion in the 19th century.

The Men Who Lost America: British Command during the Revolutionary War and the Preservation of Empire

Andrew O'Shaughnessy

Oneworld, £30, 466pp