BRUSSELS — NATO insists its new-look command structure will help the Western alliance deal with the “most serious security challenges in a generation.”

Though full details are yet to be confirmed, the organization is revamping its structures partly to better counter the perceived threat posed by Russia.

Defense ministers agreed to a preliminary design for adapting the alliance’s command structure at their meeting in November.

This includes a new command for the Atlantic — focused on secure sea lines of communication between North America and Europe — and a command to improve military mobility within Europe.

Allies also agreed to set up a new cyber operations center to help integrate cyber into NATO’s planning and operations at all levels.

An internal NATO report highlighted the reduced command structure as a key factor in undermining the alliance’s capabilities.

Concerns have also been voiced recently about NATO’s ability to rapidly move troops and equipment around mainland Europe, particularly after Russia’s annexation of Crimea from Ukraine in 2014 raised fears among Eastern members.

The need for change is spelled out by NATO Secretary General Jens Stoltenberg, who said that at the end of the Cold War, NATO had about 22,000 personnel working in 33 commands.

Today, NATO has less than 7,000 working at seven commands.

“We reduced the command structure at the end of the Cold War because tensions went down,” but now, instead of focusing on expeditionary operations, there must be a dual focus on the alliance’s presence in Europe, he said.

“NATO’s actions are defensive, proportionate and in line with our international commitments. Our aim is not to provoke conflict, but to prevent conflict,” the Norwegian official added.

Stoltenberg said the new logistics command will be an improvement, but warned that civilian government cooperation was still needed to overcome administrative hurdles such as customs rules.

“This is not only about commands,” he said. “We also need to ensure that roads and bridges are strong enough to take our largest vehicles, and that rail networks are equipped for the rapid deployment of tanks and heavy equipment.”

A source at the Brussels headquarters said NATO had become the “most successful military alliance in the world” because of its ability to adapt.

Gen. Denis Mercier, one of NATO’s supreme allied commanders, conceded that the shake-up was also designed to address current “deficiencies.”

“To win tomorrow’s war, we have to prepare today, and this is what was behind the reorganization,” he said.

Gen. Petr Pavel, who chairs NATO’s Military Committee, said the upgrade will allow the alliance to meet its “core tasks” and meet the requirement from NATO members for a “robust and agile” command structure.

“I need to stress that this is subject to a political decision,” he added.

Also welcoming the modernization plans, Gen. Curtis Scaparrotti, NATO’s supreme allied commander Europe, said Russia’s “resurgence” underlined the need to adapt to evolving threats. And U.S. Ambassador to NATO Kay Bailey Hutchison said the Ukraine crisis had forced the alliance to consider “a more efficient operation that will work.”

NATO is still fleshing out the details of the changes.