The U.S. is flexing its military muscle in the Mediterranean. Barack Obama’s rhetoric was rather reserved up to now: The U.S. president, who had placed his credibility on the line with his “red line” speech last year, looked for reasons in his statements to not have to take action.

Obama’s short-term objective seems to have been achieved yesterday with Syria’s consent: getting, for the time being, U.N. inspectors to the site of the recent atrocities. What will be construed from the results of the investigations might well provide for a further diplomatic tug of war. But what if the U.S. and the allies clearly see Assad’s military as guilty once again? A U.N. Security Council resolution that merely condemns the use of weapons of mass destruction would be ineffective.

The U.S. president has made clear that the support of allies and legal legitimization from the U.N. must be in place before an intervention; however, it is clear that Russia would again block any intervention against its friend Assad. Berlin too would probably abstain, as in the question of Libya. Chancellor Merkel hobbles behind the events with her statement that the conflict in Syria can only be solved politically, not militarily.

The warring parties there face off more irreconcilably than ever; a political agreement appears to be impossible. Now the international debate centers on effective deterrence to prevent further atrocities — just like Kosovo in 1999.

Nevertheless, especially with a view of the Middle East, the danger appears significantly greater that military action would have consequences beyond Syria, as the most recent words from Iran and Israel demonstrate. But Assad should not underestimate Barack Obama. Even the winner of a Nobel Peace Prize could have a threshold of tolerance — and the moral duty to act.