Defenders of the President's inaction have always claimed that all the proposed lines of action in Syria, from bombing Assad's airforce to arming the rebels, are risky. Tragically for Syrians, and now for Iraqis, and perhaps soon enough for the rest of us, the consequences of a failure to act were given far too little weight. Regime brutality against the majority Sunni population of Syria and intervention by foreign Shia forces (Iranian and Hezbollah) have attracted a far larger and more dangerous group of jihadis than ever existed in Afghanistan, one whose threat to European and American allies and interests keeps growing. That the Iranian and Hezbollah intervention has elicited no serious American response has not only favoured the regime's survival but shaken faith in American reliability among all US allies in the region and beyond it. That Iran has appeared far more determined to win in Syria, defined as keeping Assad in power, than the US has appeared in achieving its stated goal (that Assad must go) similarly shakes confidence in American power and willpower. The last-minute reversal in the summer of 2013 about bombing Syria made the US appear uncertain and unreliable, if not quixotic. The huge and growing refugee burdens threaten stability in Jordan, long a key American ally, and in Lebanon. And the fact that Assad is an Alawite trying to rule a 74 per cent Sunni country suggests that with him in power there will never be stability, only more war — in Syria and Iraq, and presumably elsewhere soon enough unless the contamination is fought.

Less tangibly but of equal importance, America's willingness to enforce the norms of international conduct has been undermined, as has American moral leadership. Pledges such as "never again" and doctrines such as the "responsibility to protect" are worthless without an American commitment behind them. The complete lack of reaction to Assad's continuing use of chemical weapons in 2014 undermines both the viability of the ban of chemical weapons and the belief that the US is willing to enforce such rules. Older rules against armed aggression, enforced by the US when it led a coalition of states to restore Kuwait's sovereignty and independence, are unlikely to survive without American insistence. And the association of the US with the cause of human rights and democracy, going back at least to Woodrow Wilson, has been weakened by Obama's unwillingness to act in the Syrian case. America's soft power is linked to its reputation for idealism and the defence of human values. The refusal to use hard power in the Syrian case has contributed to a diminution of "soft power" as well.

What can the US and its European allies actually do at this juncture about Syria? Another grand diplomatic effort is useless now. The efforts made by the US in Geneva to reach a political accord did not succeed because diplomacy will always reflect the power relationships on the ground. It is those that must be changed, by strengthening the anti-Assad, anti-jihadi forces composed of nationalist Syrian rebels.

First, if we are serious about toppling Assad, defeating Iran in a proxy war, and building a rebel group stronger than the jihadi groups, we must establish a large, serious, coordinated and multi-national programme to train and equip those rebels. Their weakness is largely linked to their lack of guns and other equipment, and money with which to pay fighters, while jihadi groups appear to have far more of both. The balance of forces will change when anti-jihadi groups can arm and train all the men they can attract, including attracting them from other forces which were able to feed and clothe them and supply modern weapons. This must come first because without such a fighting force, there is no hope that the power of the regime or the jihadis can be countered. The only other possible outcomes are continuing war, with more deaths and more refugees and with a further metastasising of jihadi forces, or an Assad victory. These outcomes should be unacceptable to us.