The combined impact of austerity-era cutbacks and spending choices has hit the British Army the hardest of all the services. Now smaller than at any time since Waterloo, it has failed to meet even modest recruitment goals, in part because of an embarrassing effort at outsourcing. It is still several thousands short of its goal of 82,000 “fully trained regular army soldiers,” despite downgrading what it means to be “fully trained,” as well as falling short of its goal of 30,000 in the army reserve.

In other areas of modern warfare, however, Britain’s capacities are more highly regarded, especially in cyberdefense and cyberoffense, intelligence and space.

Tom Tugendhat, a lieutenant colonel in the army reserves who served in Iraq and Afghanistan and is now chairman of Parliament’s Foreign Affairs Committee, said: “The fundamental problem in defense is always personnel. Our army and navy are too small, and our reserves are not even vaguely close to being fully manned,” partly because of the new carriers and nuclear submarines.

But the big-ticket items are a measure of British resolve, he said. “The U.K. will be the only European country with two aircraft carriers, the ability to deploy force and the willingness to do it,” he added. Island Britain “has always used a heavy navy to project a light army,” while Continental forces usually have the reverse.

NATO may complain about Britain’s not providing territorial forces to deter Russia, “but it’s Germany that should be providing them,” he said.

In Tallinn, the Estonian capital, the defense minister, Juri Luik, praised the British presence as a symbol of solidarity. Estonian troops fought in a British brigade in Afghanistan, he said, “so it’s a close relationship.”

Whatever their current shortcomings, Mr. Luik said, “the British have a real military culture. They understand a battle is a battle. And they can take casualties.”