A handful of spunky ex-soldiers, led by John Krasinski, step into the breach when Islamist militants attack two US compounds in the Libyan port of Benghazi.

Based on real events from 2012, this gung-ho war movie plunges us into the heart of battle when director Michael Bay unleashes a terrifyingly explosive battery of cinematic pyrotechnics.

The good guys, six private security contractors working for the CIA, mostly sport big muscles, even bigger beards and go by such names as ‘Rone’, ‘Tanto’, ‘Tig’ and ‘Bub’ (James Badge Dale, Pablo Schreiber, Dominic Fumusa and Toby Stephens).

The bad guys are not only the mostly faceless, gun-toting Arabs doing the attacking, but also the heroes’ pussyfooting CIA superiors. These Yale and Harvard brains treat the brawny alpha males under their command with open condescension (‘You’re the hired help’) and their lily-livered indecision puts US lives in jeopardy when the crisis escalates.

Indeed, for many, the film’s most rousing moment is not when the men repel their remorseless assailants, but when one of their number tells the local CIA chief: ‘You’re not giving orders any more. You’re taking them. You’re in my world now.’

Bay buys into the notion of the USA as the world’s reluctant policeman without a qualm and his film’s view of its heroes is blatantly sentimental. But when it comes to the combat scenes, and to the nerve-shredding suspense sequences leading up to them, it is stunningly effective.