Cruise missiles alone cannot secure credibility Viewed from Washington, the Syrian crisis has been only partly about chemical weapons. The other crucial commodity at stake was American "credibility" - that mystical quality on which US and global security is often deemed to depend. A Russian diplomatic initiative has saved Barack Obama from the prospect of a humiliating defeat in Congress over Syria. Yet the entire episode has left the impression that America's president, politicians and public are increasingly reluctant to deploy military force - even when a US "red line" has been crossed. That has raised worries that America's rivals, from Iran to China, will soon be tempted to test US resolve. This possibility is certainly there. Yet those who worry that US power rests on the nation's willingness always to enforce its red lines are taking too narrow a view of what "credibility" means for a great power. The willingness to honour security commitments is just one element. Not making terrible mistakes in foreign policy is another crucial part of credibility - as is the preservation of a strong economy and an attractive society. The biggest blows to US global power and prestige in the past decade were inflicted by the Iraq war and by the financial crisis of 2008. Neither had anything to do with an unwillingness to defend a red line or a reluctance to fire off cruise missiles. Indeed, one lesson of Iraq was that ill-conceived military intervention can be far more damaging to US power than any hesitancy about the use of force. In fact, arguably the two biggest blows to American global standing in half a century both flowed from mistaken military interventions, with Iraq repeating some of the damage done by Vietnam. By contrast, the biggest triumph for US foreign policy - the collapse of the Soviet empire - was achieved without a shot being fired. For conservatives, Ronald Reagan is the epitome of a strong president - just as Jimmy Carter, and now Mr Obama, epitomise weakness. Yet, while Reagan certainly increased defence spending, he was very wary of actually deploying troops. The boldest mission for the military under Reagan was the invasion of Grenada - population 90,000. When 241 US servicemen were killed by a bombing in Lebanon in 1983, Reagan pulled American troops out. The aerial bombardment of Libya during the Reagan years was a short punitive strike, with no thought of regime change - rather similar to what Mr Obama was planning for Syria. In the end, the strength that mattered in the Reagan years was a domestic economic revival, which helped to restore US confidence and prestige at a time when the Soviet economy was falling apart. Mr Obama has certainly grasped the point that US global strength ultimately rests on the strength of its economy - witness his oft-repeated insistence that America needs to concentrate on "nation-building at home." The rise and fall of other global hegemons in the past century reinforces the point. The decline of Britain, France and the Soviet Union was caused by the fact that their economies were too weak to sustain their international commitments. In all three cases, the cost of fighting wars had sapped the nation. The USSR's intervention in Afghanistan was one of the final nails in its coffin. Britain's ability to sustain an empire was in effect ended by the costs of the second world war. And the strength of postwar France was undermined by ill-fated wars in Algeria and Indochina. With China soon to surpass the US as the largest economy, America cannot assume that it is able to afford to make costly military mistakes long into the future. But Mr Obama's determination to avoid new foreign conflicts was shaken by Syria's use of chemical weapons. The president and his team were genuinely horrified by the use of poison gas - and also wanted to demonstrate America's red line meant something. Mr Obama attempted to reconcile his call for a military response with his own anti-interventionist instincts by repeatedly emphasising how limited his plans were - "unbelievably small" in the words of John Kerry, secretary of state. But sceptics raised the obvious questions about what such a limited strike would achieve; and whether one intervention would lead to another. The Syrian crisis is a classic hard case - with strong arguments on both sides of the debate. And although Mr Obama steered a wobbly course, his threat to use military power was nonetheless made - and did force a shift in the positions of both Russia and Syria. For while it is possible that President Vladimir Putin of Russia was prompted to make his diplomatic initiative because of a hitherto unnoticed generosity of spirit towards Mr Obama, it seems more likely Moscow moved fast because it was genuinely alarmed by the prospect of US military action in the Middle East. In that sense, for all his fumbling, Mr Obama's threat of military action was effective. It would certainly be a foolish nation that concludes Washington's failure immediately to fire missiles at Syria means that US military power is now permanently off the table in international affairs. America remains the pre-eminent military power in the world - with a long history of armed interventions. The fact that Mr Obama is determined to use greater caution and deliberation before taking military action need not detract from American credibility. It may help to preserve it.