Aircraft carrier HMS Prince of Wales has set sail from Portsmouth naval base to begin a 12-month deployment leading a NATO international task group.
People gathered around the city's Round Tower on Wednesday morning to wave off the Royal Navy ship in what is her first operational deployment.
The £3.1bn vessel will act as the command ship for the naval element of NATO's Response Force, formed to rapidly deal with major global events.
The deployment comes amid heightened tensions between NATO and Russia, and increasing fears of a possible Russian invasion into Ukraine.
HMS Prince of Wales' Commanding Officer, Captain Steve Higham said ahead of leaving Portsmouth that the "challenge and the threat posed by Russia" has already been signposted.
"Our job here on Prince of Wales is to be ready to respond, to provide the maximum amount of capability and flexibility," he told Forces News.
The Royal Navy formally assumed command of the maritime part of the NATO Response Force during a ceremony on board HMS Prince of Wales on Tuesday.
The aircraft carrier, which will operate across the Atlantic, northern Europe and the Mediterranean during the deployment, will now take part in a series of exercises.