LONDON (AP) — The head of Britain’s armed forces has warned that the world stands at the cusp of a “third nuclear age,’’ defined by multiple simultaneous challenges and weakened safeguards that kept previous threats in check.

Admiral Tony Radakin, chief of the defense staff, said Britain needs to recognize the seriousness of the threats it faces, even if there is only a remote chance of Russia launching a direct nuclear attack on the U.K. or its NATO allies.

While the Cold War saw two superpowers held at bay by nuclear deterrence and the past three decades were characterized by international efforts to restrict the spread of nuclear weapons, the current era is “altogether more complex,” Radakin said Wednesday in a speech to the Royal United Services Institute.

“We are at the dawn of a third nuclear age…’’ he said. “It is defined by multiple and concurrent dilemmas, proliferating nuclear and disruptive technologies and the almost total absence of the security architectures that went before.”

Challenges faced by the West include Russia’s threat to use tactical nuclear weapons in Ukraine, China’s drive to build up its nuclear stockpiles, Iran’s failure to cooperate with international efforts to limit its nuclear program, and “erratic behavior” by North Korea, Radakin said. All of this comes against a backdrop of increasing cyber-attacks, sabotage and disinformation campaigns aimed at destabilizing Western countries.

He described the deployment of North Korean soldiers alongside Russian forces on Ukraine’s border as the year’s “most extraordinary development,’’ and warned that further deployments were possible.

The annual lecture by the chief of Britain’s defense staff is a tradition at RUSI, one of the country’s foremost think tanks on military and strategic issues.

Radakin used the lecture to make the case for continued reforms in the British military so the U.K. is prepared to respond to the changing international landscape. That includes maintaining Britain’s nuclear deterrent, which is “the one part of our inventory of which Russia is most aware and has more impact on Putin than anything else,” he said.

Britain keeps at least one submarine armed with nuclear missiles at sea at all times so that it can respond in the event of a nuclear attack.

The U.K. government is currently conducting a strategic defense review to determine how its armed forces should be staffed and equipped to confront the new challenges. The results are due to be published in the first half of next year.