India, March 25 -- In November 2012, then National Security Advisor (NSA) Shivshankar Menon and I met President Barack Obama's NSA Tom Donilon in Phnom Penh on the margins of the East Asia Summit. With the Arab Spring raging and Syria descending into internal conflict, Menon asked Donilon how Sunni fighters from Afghanistan and Pakistan were reaching Syria, with land access across Iran and Iraq denied, warning that a destabilised Syria would turn into a worse terrorist sanctuary than Afghanistan.

Donilon replied that the US would first get rid of (Syrian President) Bashar al-Assad, then deal with terrorism. Assad would last until December 2024, but a devastated Syria became a sanctuary for virulent terrorist groups such as ISIS and Al Nu...