Far from uniform
A POINT OF VIEW
In both the US and UK, civilian leaders have the upper hand over the military - but the two countries have very different attitudes to veterans reaching the top, says David Cannadine in his Point of View column.
The recent decision by President Barack Obama to accept the resignation of General Stanley McChrystal and to replace him with General David Petraeus caused a predictable media storm on both sides of the Atlantic.
But taking the long view of American history, there's nothing particularly unusual about the president, as commander in chief of the US military, asserting his authority over the armed forces in this way.
In the aftermath of the departure of Gen McChrystal, several commentators rightly noted that in April 1951, Harry S Truman had sacked Gen Douglas MacArthur after he had publicly criticised the president's limited war strategy in Korea.
As with Truman's earlier decision to authorise the dropping of atomic bombs on Japan, it was highly controversial, though no one contested his constitutional right to make it.
And long before that, in November 1862, President Abraham Lincoln dismissed the equally popular George McClellan from his command of the Northern Army during the American Civil War, because he'd failed to deliver victory over the south. Two years later, McClellan stood against Lincoln for the presidency, but he went down to defeat.
These three examples are a vivid reminder that in the United States, the military is subordinate to the civilian authority; but as so often in America, things are never quite as straightforward as they seem.
After all, the first President of the United States was none other than George Washington, whose fitness for that post depended almost entirely on his achievements in having beaten the British on the battlefield during the War of Independence.
Two of America's most famous 19th Century presidents had also been generals earlier in their careers: Andrew Jackson, who defeated the British at the Battle of New Orleans in 1815, and Ulysses S Grant, who was a much more successful leader of the northern armies during the Civil War than George McClellan, and who never lost the support of Abraham Lincoln.
And Harry Truman's successor as American president was another general, Dwight D Eisenhower, who had been supreme allied commander in Europe during the closing stages of World War II.
In modern times, former military leaders have occupied the White House much more frequently than they have resided at 10 Downing Street, where the last such figure to do so was the Duke of Wellington, as far back as 1828.
And sometimes, although not always, a good war record has helped propel other aspiring a candidates to the American presidency.
This was certainly true for John F Kennedy in 1960, and it may have assisted George Bush senior in 1988.
But this isn't invariably the case. Four years later, the same George Bush was defeated by Bill Clinton, who had successfully evaded military service at the time of the Vietnam War; while in 2004, George Bush junior, who had also avoided combat, decisively vanquished John Kerry, who had fought with great distinction in Vietnam.
Nor, in 2008, did the brave resume of John McCain help him in his unsuccessful bid against Barack Obama. So while a military background may sometimes help American presidential candidates, it's no guarantee of electoral victory.
Although more American presidents have held high command than British prime ministers, there were some 20th Century occupants of 10 Downing Street who had first-hand experience of fighting.
Four future prime ministers served in the trenches during World War I: Winston Churchill, Clement Attlee, Anthony Eden and Harold Macmillan.
As a descendant of the first Duke of Marlborough, and as someone who had fought in India and Africa, Churchill had a high - perhaps excessive? - opinion of his skills as a military strategist; and like Lincoln, he didn't hesitate to sack his generals if they failed to deliver him the victories he craved - as Auchinleck and Wavell both found to their cost.
And Harold Macmillan, who was another former army officer, could never conceal his contempt for those politicians who hadn't been in combat, such as Rab Butler and Hugh Gaitskell.
Among later prime ministers, Edward Heath was commissioned in the Royal Artillery and ended World War II as a major, while James Callaghan joined the Royal Naval Volunteer Reserve as an ordinary seaman.
Callaghan would later claim that much of the cross-party camaraderie which he believed existed among members of Parliament during his time was derived from their shared experiences of being in the armed forces.
But since the 1980s, the generation of Heath and Callaghan has mostly died off, and scarcely any of today's MPs have seen active duty in the army, the navy or the RAF.
Indeed, I'm willing to hazard the view that at no time during its modern history have there been so few members of the House of Commons, or even of the House of Lords, with military experience as they are today.
And this in turn may help explain why, during both the second Iraq War, and also with the continuing conflict in Afghanistan, relations between political leaders and service chiefs have been neither as close nor as cordial as in earlier times. The common experiences and the shared point of view are just no longer there.
Nevertheless, the fact remains that in Britain, as in the United States, the armed services are firmly subservient to civilian authority, and that ever since the time of Oliver Cromwell, the British have been deeply suspicious of military adventurers.
But this healthy scepticism isn't something that Britain has always been able to hand on to her former imperial realms when they became independent. In 1947, the Indian sub-continent was partitioned, and so was the Indian army, between India itself and Pakistan.
Since then, the Indian military has been kept successfully under civilian control; but in Pakistan, by contrast, some form of army rule has often been the norm, and to this day, democracy there remains a fragile flower.
And in some former British African colonies, military dictatorship has also reared its ugly and brutal head: in Uganda under Idi Amin during the 1970s and in Nigeria during the 1980s and 1990s.
For much of the 20th Century, and in many parts of the world, military rule, or rule by military men, has been a widespread phenomenon.
Several Latin American countries have suffered in this way, among them Argentina under General Peron and again at the time of the Falklands War, and Chile under General Pinochet.
Even here in Europe, such figures have been in power more often than you might think. From 1920 to 1944, the dictator of Hungary was Admiral Horthy: a strange title, indeed, for Hungary was a completely landlocked nation, with no navy whatsoever.
Spain was ruled by General Franco from the time he emerged victorious in the civil war until his death; Greece was in the hands of a military junta from 1967, when the monarchy was overthrown, until 1974, when a democratic republic was established; and in France, Marshal Petain and General Charles de Gaulle represented two very different styles of quasi-military leadership.
There's been nothing in Britain to compare with any of this. But in 1968, which was a low point in the Labour government of Harold Wilson, an unsuccessful attempt was made by Cecil King, the eccentric and wayward newspaper tycoon, to plan for some sort of military coup.
King feared that law and order would soon disintegrate, and that the army would have to intervene. In that event, he hoped to persuade Admiral of the Fleet Lord Mountbatten to take over as head of a government of national unity.
As the last Viceroy of India, Mountbatten had presided over the partition of the Indian army, and he much regretted Pakistan's subsequent lapse into dictatorship. A decade later, when he was First Sea Lord at the time of Suez, he did everything he could to make known his opposition to British intervention, but his sense of duty prevented him from resigning. By 1968, Mountbatten was retired, but he continued to believe that in Britain the armed forces should stay out of politics.
In the United States, by contrast, retirement frees up military men to make a legitimate bid for the White House.
I wonder if such thoughts, and such ambitions, are already forming themselves in the mind of Gen McChrystal? Or might he fear that, if he did run for the presidency, he would merely suffer the same fate as that which earlier befell Gen McClellan?