An Officer's Commission (known in the Commonwealth armed forces as a Queen's Commission) is an authorisation, from the Government of the day, to command troops. In Britain, such commissions are granted to members of the armed forces who have completed a prescribed course of military training at an approved Military Academy - usually the Royal Military Academy at Sandhurst (RMAS). In Australia, a similar system revolves around the Royal Military College of Australia at Duntroon, in Canberra. The Canadian Armed Forces have their own Royal Military College. In the United States, West Point is the starting point for most officers in the US Army.
Leadership in the British Army was not always on merit. Early English armies were simply militias formed by peasants and serfs, officered by fit and motivated (but not always militarily knowledgeable) knights and barons. The British Army today does not carry the title "Royal" for precisely this reason. It consists mostly of regiments which were originally raised in tribal fashion, based on baronial loyalties, and withheld from Royal service until political kickbacks had been obtained.
The English Civil Wars of 1642-1652 saw the success of a more egalitarian military practice: the New Model Army of Gen Thomas Fairfax was commanded by officers promoted on merit rather than birthright. The success of Oliver Cromwell's forces planted a seed of ambivalence in the British military mind. Although the cavalry general Cromwell was careful to resign from the military before assuming his role of Lord Protector of the Commonwealth, the Army remained the guarantor of his power for an uncomfortably long time. This is the nearest that Britain has ever come to a military dictatorship - although Cromwell's stewardship of the realm was, on the whole, responsible and beneficial.
Following the Restoration, the practice of buying commissions was quietly reintroduced. It was felt that only men with a financial stake in the country, would be motivated to fight for its preservation. Thus did the small professional expeditionary force of the British Army go to war in 1854 in the Crimea. With the exception of such sturdy warriors as Brigadier-General The Honourable James Scarlett, the British military leadership was proved totally incompetent on numerous occasions. The Light Brigade rode to disaster only hours after Scarlett's Heavy Brigade had spectacularly routed the vastly more numerous Russian heavy cavalry.
The Cardwell Reforms in 1871 abolished the buying of commissions, and compelled aspiring leaders to attend the Military Academies, which resulted in establishment of the Academies as the arbiters of military excellence. Today, Sandhurst stands as a symbol of military achievement for leaders in the British Army, as well as for overseas graduates.
King Abdullah of Jordan, for example, followed in the footsteps of his father King Hussein as a graduate from Sandhurst. More recently, Princes Harry and William have been commissioned following their respective Sandhurst cadetships. (Ironically, Prince Harry is militarily senior to his elder brother, despite Prince William being next in line for the Throne after their father, Prince Charles.)