When the Chilean director Raul Ruiz died in August last year, he left a heaving back catalogue of more than 100 features plus one final, unfinished flourish: an epic historical pageant about the 1810 battle of Bussaco.

Now Linhas de Wellington (The Lines of Wellington) — “conceived by” Ruiz and completed by his wife, the film-maker Valeria Sarmiento — has finally been completed, marching into the Venice film festival with muskets blazing and colours flying. For all its faults, it’s full of life.

Ruiz and Sarmiento’s film recounts the tale of the Napoleonic invasion of Portugal and the withdrawal of Wellington’s Anglo-Portuguese forces to the southern hill country.

The general’s devastating tactic was to compensate for his army’s comparative lack of numbers by luring the French into hostile terrain, fortifying the lines of Bussaco and picking the invaders off as they climbed the slopes.

And yet the Wellington we see here is hardly the all-seeing genius we know from popular history. Played by John Malkovich, he comes across as a preening little despot, more concerned with publicity than practicality.

Wellington is concerned about the battle scenes daubed by his official army painter, and wants “more panache” and fewer corpses. His mind’s not really on the job in hand. Instead, Linhas de Wellington salutes the supporting characters, the unsung heroes. It shows us the human drift of the retreating army, serviced by satellite industries of merchants and whores. Nuno Lopes plays the decent, rough-necked Portuguese sergeant in a yarn that jolts from high-flown romance to swashbuckling adventure to bawdy, unreconstructed farce.

Upstairs in the captain’s quarters, an English teenager (Victoria Guerra) merrily reassures one of Wellington’s officers that it’s entirely fine, they can do what they like, because she has lost her virginity already and that there’s surely nothing wrong with that.

In stuffing the ranks with former Ruiz collaborators (Malkovich, Catherine Deneuve, Isabelle Huppert, Michel Piccoli), Sarmiento sometimes risks spinning the film into an overstuffed revue show, pulling in too many directions. For all that, she delivers the tale with a gusto that would have made Ruiz proud.

Linhas de Wellington now finds itself battling the likes of The Master, Betrayal and Fill the Void for the festival’s top prize this weekend.

It won’t win; it’s hopelessly outgunned. But this rambunctious, rollicking affair sends its creator off with full military honours. — The Guardian, London