The locals had no idea what it was the Israelis dropped on the Syrian military base at Bimalkah. They just knew it produced a series of almighty and rather terrifying explosions.

So powerful was the biggest blast that it sheared trees in half along the road outside the base, rattled windows in the city of Tartus eight miles away and fooled nearby seismic sensors into believing there had been a magnitude three earthquake.

Ever since the fall of Bashar al-Assad, Syria’s president, Israel has mounted a sustained campaign to eliminate much of the old regime’s military capability, a precaution, it says, against sophisticated weaponry falling into the hands of hostile Islamists.

The attack on Bimalkah in the early hours of Monday morning was among the most powerful of the more than 450 air strikes the Syrian Observatory for Human Rights calculates Israel has launched over the last nine days. The organisation, based in Britain, has documented military action in Syria since the uprising against Assad began in 2011.

What exactly was inside the base, the rebels guarding it on Monday could not say exactly. They knew it housed an air defence facility and missile warehouse and that, certainly until a few days earlier, it also stored a formidable amount of Russian weaponry.

The commander standing guard outside the smouldering base said he also believed that the stockpile housed a large Hezbollah arms dump.