Thousands of sailors and marines and a flotilla of warships from Britain and France are on manoeuvres in the Mediterranean in preparation for combined operations around the world.
Codenamed Corsican Lion, the operation - the biggest since the two countries signed a military cooperation treaty in 2010 - is designed to get both sets of troops used to each other's fighting methods.
The exercise, which involves 6,000 service personnel, is using a range of vessels from both navies, although the centrepiece is the French aircraft carrier Charles De Gaulle and her fast jets.
Her presence has re-ignited the controversy over the scrapping of the UK's own carriers almost a decade before their replacements will be in service.
The Defence Secretary, Philip Hammond, who flew in to observe the exercise and hold bi-lateral talks with his French counterpart, Jean-Yves Le Drian, faced a barrage of tricky questions from reporters about the potential embarrassment of the UK having to go cap in hand to her allies to provide carrier cover in the meantime.
Mr Hammond insisted that tough decisions had had to be made and that the new Queen Elizabeth class British carriers would provide an enhanced capability when they came on stream at the end of the decade.
"As I stand on the deck of the Charles De Gaulle, I shall be remembering that we are building two brand new modern carriers," he said.
The commander of the UK Response Force Task Group, Commodore Paddy McAlpine, said the combination of land, sea and air abilities means that in any future deployment, anywhere in the world, "we are the crystal everything else forms around".
The week-long exercise involves not only five British naval ships but Royal Marines from 3 Commando Brigade and their French counterparts.
Air support comes from French Rafaele and Super Étendard jets and dozens of helicopters ranging from Apaches to Sea Kings and Chinooks.
On the water, small boats and landing craft allow the Marines from both sides of the Channel to practice their drills.
It is not without its problems though.
French Lieutenant Benoit Bouquin said: "It's very interesting for us because we can use all the British boats, but quite difficult with the language. Not many of our soldiers speak English."
Few Royal Marines speak French either, although Corporal Ben Cussons says they manage to communicate.
"On the shop floor, you just make do," he said. "It's all smiles and nods and 'hellos'. At our level, that's enough."
Once Corsican Lion is complete the fighting flotilla will move on to the Adriatic and further exercises, this time with the Albanians.
That exercise is imaginatively tagged "Albanian Lion".