[A] U.S. airborne raid into Syrian territory marks the culmination of years of frustration with Damascus' reluctance to police its own border with Iraq, the main point of entry for foreign jihadists.
The Sukkariyeh Farm, which U.S. forces raided, is just over the border from the Iraqi city of al-Qaim, which, since 2003, has been a key funneling point for jihadists entering Iraq.
Syria is a linchpin in the region, providing a link between Tehran and the Lebanese militia organisation Hezbollah. While it is a secular regime, Syria has allowed extreme Islamist groups to operate from its territory, using them both as an internal political pressure valve and to tie down US forces inside Iraq.
A raid into sovereign territory would have needed high-level U.S. clearance and may have been intended as a warning to Syria that it is not inviolate and must choose carefully whom it supports.