The US airborne raid into Syrian territory marks the culmination of years of frustration with Damascus’s reluctance to police its own border with Iraq, the main point of entry for foreign jihadists.

Since the 2003 invasion, Syria, fearing that it could be the next target for regime change, has allowed Islamic militants to cross its desert borders freely. Significantly, the village of al-Sukkari farm, which US forces raided, is just over the border from the Iraqi city of al-Qaim, which, since 2003, has been a key funnelling point for jihadists entering Iraq on the so-called rat run to the Sunni cities of Ramadi, Fallujah and, finally, Baghdad.

But a raid into sovereign territory would have needed high-level US clearance and may have been intended as a warning to Syria at a time when America and Israel are trying to turn the regime of President Assad away from Iran and into peace talks.

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.

It has also sought maximum strategic return for its allegiances, keeping its close economic ties with Iran while simultaneously conducting indirect negotiations with Israel, through Turkish mediators.

Besides economic and diplomatic incentives to return to the international mainstream, military pressure has also been used against the Syrian regime. In September last year, Israeli war planes carried out a daring raid deep into Syrian territory to destroy what some Western officials suspect may have been a fledgeling nuclear or chemical weapons facility.

Despite making threats, Syria did not retaliate against Israel. Instead it continued to negotiate in secret on a possible peace deal that would lead to the return of the Golan Heights.

The repressive but normally stable Syrian regime has also been rocked in recent months by a series of high-level assassinations and bombings, some blamed on Israel, others on the jihadists.

While US commanders may have calculated that a cross-border raid was tactically necessary to tackle Islamist extremists using Syrian territory, the attack also sent a tough strategic message to Syria that it is not inviolate and must choose carefully whom it supports.

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