In the future, the indecent haste with which Barack Obama sought cover under the umbrella unfurled by his Russian counterpart, Vladimir Putin, in the Syrian chemical weapons crisis will be viewed as a watershed moment when it comes to America’s waning power in that region. In the aptly named “arc of instability,” the lands from the Chinese border to northern Africa that President George W. Bush and his neocon acolytes dreamed of thoroughly pacifying, turmoil is on the rise. Ever fewer countries, allies, or enemies, are paying attention, much less kowtowing, to the once-formidable power of the world’s last superpower. The list of defiant figures—from Egyptian generals to Saudi princes, Iraqi Shiite leaders to Israeli politicians—is lengthening.