The Baltops 16 operation – one of the North Atlantic military alliance’s largest drills in northern Europe – aims to reassure nations lining Russia’s western border of Nato’s commitment to the security of the Baltic Sea region.

Fears are growing across the Baltics and the wider region of a repeat of the annexation of Crimea in 2014, when Russia used the guise of a military exercise to grab land from Ukraine.

The UK was among 15 Nato nations plus Finland and Sweden to practise the amphibious assaults, which concluded yesterday.

The Royal Navy’s HMS Ocean was in the Baltic Sea leading the exercise, which has seen Royal Marines Commandos perform a beach assault in scenes reminiscent of the Normandy landings.

Two Cold War-era B52 bombers also performed dummy mine laying drills over the Baltic Sea.

Around 6,100 maritime, ground, and air force troops took part across Estonia, Finland, Germany, Poland, Sweden, and throughout the Baltic Sea.

The maritime exercise is followed by Rimpac, the Rim of the Pacific Exercise, which is the world’s largest international maritime warfare exercise off the coast of Hawaii.

A British contingent will join 25,000 personnel coming from 27 nations with 45 ships, five submarines and more than 200 aircraft.

Significantly, the Chinese Navy have been invited to take part in the exercise, despite heightened tensions in the South China Sea.

Chief of US Naval Operations Admiral John Richardson said: “The invitation is still there for the Chinese to participate in Rimpac and these are the sorts of things that sort of bring us all together in positive, constructive ways.”

Rimpac will test responses to challenges from disaster relief and maritime security operations to sea control and complex combat operations.

America insists increased US and Nato exercises in eastern Europe are necessary steps to train with allies and deter the most aggressive Russian maritime expansion in 30 years, and do not amount to “sabre-rattling”.