Codenamed Operation Destined Glory/Loyal Midas, the two-week training exercise of Nato's Reaction Force has the navies of 10 member nations and 8500 servicemen participating.
In this wargame, tanks, helicopters and even Harrier jets are attempting to take control of a fictitious rebel-held territory in one of the largest amphibious exercises of the year.
But this is no fiction for the fishermen of Capo Teulada and Sant'Antioco, 400km south of Rome, who have witnessed their fishing areas and a military base near their town "invaded".
On 4 October, 10 small fishing boats defied the ban on sailing in the area which had been declared an off-limits military zone, and blockaded the naval warships.
The protest quickly gained popularity. Within a week, the number of protesting fishing boats reached 42, stopping part of the naval exercises originally scheduled to conclude on 14 October.
"We don't want a donation, we just want to work... Because they don't allow us [to] work, we're staying here"
It is not the first time Nato has been met with an unfriendly welcome in Capo Teulada.
Last year a similar exercise attracted protests. Then, the fishermen of Capo Teulada said they wanted to be able to fish all year round and not be forced to steal to make a living.
The local government struck a compensation deal with those fishermen only last month. Now people from neighbouring towns say they are also affected and are seeking a similar compensation package.
But on Tuesday, one fisherman told Italy's local RAI Tre TV: "We don't want a donation, we just want to work... Because they don't allow us [to] work, we're staying here."
On board the Italian naval ship, ITS Mount Etna, Lieutenant-Commander Marco Maccaroni is convinced the protesters are just after money.
"We don't feel it's just against us, it's a way to take the attention of the Italian government," he says. "If you're fishing in the sea without disturbing anybody, no one will know."
It only takes a single fishing boat to disrupt the exercise. Once a non-shooter enters the training area, the area becomes "fouled" and all shooting has to stop.
Lieutenant J D Sullivan told Aljazeera.net he did not believe that it was much of a problem: "Instead of pushing the button, you do all the things up to pushing the button, so you go through the whole process, a 'cold-run'."
Nato commanders say they have
a Plan B for the exercise
The safety of the protesters is Nato's priority according to Civilian-Military Cooperation officer Commander Vito Minuado: "Our line is not to touch anybody, they're not the enemy, it's not our intention to use force, it's an exercise."
But Minuado thinks it is actually locals who will lose out.
"We can help the economy of Sardinia - 8000 people going to restaurants in Cagliari [Sardinia's capital] over three days," he said.
"We use [the sea] for just 10 days a year and [locals] get paid."
The Nato Response Force, which lives by the motto "always ready" has a Plan B: Bring the marines to the beach by road, instead of using boats to get them from the ships onto land.
"If we have any problems, we have an alternate plan. This is a little complication," explained Rear Admiral Salvatore Ruzittu, the second in command of the whole exercise.
On board command ship the ITS Etna, this mock conflict has just become very real.
Either the land assault - a year in the making - will go ahead as planned, or a small group of fishermen will have scored an unthinkable victory.