NATO has assumed command of aircraft carriers three times this year in order to practice integrating national forces under alliance leadership, an often overlooked capability that experts and officials say is vital for NATO to operate effectively in wartime.

Naval Striking and Support Forces NATO took control of the Harry S. Truman carrier strike group from the US Navy's Italy-based Sixth Fleet as part of the NATO-led exercise Neptune Strike 2022.

Vice Adm. Gene Black, who commands both Sixth Fleet and Naval Striking and Support Forces NATO, said at the time that the handover demonstrated the power and cohesiveness of our maritime forces and the NATO alliance.

Black's NATO command assumed control of the Truman strike group as part of Neptune Shield 2022, which focused on overcoming the complexity of integrating command and control, according to a release.

MH-60S Sea Hawk helicopter Cavour aircraft carrier
A US Navy MH-60S Sea Hawk helicopter alongside the Italian Navy aircraft carrier ITS Cavour in the Adriatic Sea during Neptune Strike 22, February 2, 2022.
US Navy/MCS3 Tate Cardinal

NATO assumed command of the Italian aircraft carrier and its strike group at the end of May, making it the first NATO aircraft carrier strike group.

The deputy commander of Naval Striking and Support Forces NATO said that integrating with Cavour removes artificial seams between the maritime and air domains.

NATO called the exercises — which were called —vigilance activities.

Naval Striking and Support Forces NATO is unique in that it provides a separate, direct line of control from the command to specific strategic forces, according to Joshua Tallis, a research scientist at CNA.

Tallis, an expert on naval operations, told Insider that that allows Wolters to maneuver those high-value units across the theater as a responsive force in a way that is largely unparalleled elsewhere in NATO.

From right to left, Nimitz-class aircraft carrier USS Harry S. Truman (CVN 75), the Italian aircraft carrier ITS Cavour (C 550) and the French aircraft carrier Charles de Gaulle (R 91) transit the Mediterranean Sea in formation, Feb. 6, 2022.
USS Harry S. Truman, right, ITS Cavour, center, and the French aircraft carrier Charles de Gaulle in the Mediterranean Sea, February 6, 2022.
Bela Chambers/U.S. Navy

Project Neptune began in early 2021, with the goal of defining the process through which Sixth Fleet and Naval Striking and Support Forces NATO would handle the transition of warships between national and NATO command.

Tallis told Insider that Project Neptune activities have strengthened the multinational command structure that is a critical but easy-to-miss lever of NATO's combat power.

In the NATO context, it is harder to integrate air, sea, and land operations because of the large number of members who have to work with each other.

When command-and-control of US Navy ships shifts to NATO, back-end staff work is critical to that integration, Tallis said.

Mastering complexity, building cohesion

Navy Queen Elizabeth aircraft carrier
US Navy and Marine Corps aircraft over Royal Navy aircraft carrier HMS Queen Elizabeth and a US Navy landing craft, air cushion, May 17, 2021.
US Navy/Lt. Mark Nash

NATO has re emphasized being present and capable of operating around Europe, especially in areas like the Black Sea, amid heightened tensions with Russia over the past decade. The waters between Europe and North America remained open despite the establishment of NATO's newest operational-level command.

Several recent exercises featured aircraft carriers, a sign of the national and NATO interest in improving integration.

The French-led exercise Polaris, which centered on the aircraft carrier Charles de Gaulle, was joined by ships and aircraft from NATO allies.

The US Navy said that NATO allies are expanding their high-end maritime warfighting capabilities by integrating into exercises and carrier strike group deployment.

The capacity of Truman and Cavour to work as a cohesive team in defense of national and allied interests was improved by training with de Gaulle in the Mediterranean.

F-35 HMS Prince of Wales aircraft carrier Mount Whitney
F-35s fly by HMS Prince of Wales as it sails with USS Mount Whitney, left, and USS The Sullivans off the coast of Norway, March 11, 2022.
Royal Navy/LPhot Bill Spurr

The largest military exercise hosted by Norway since the Cold War was led by the sister ship of Queen Elizabeth.

Tensions in Europe and complicated life for NATO sailors have been caused by Russia's attack on Ukraine.

Truman remained in the eastern Mediterranean in the weeks before the attack to assure allies and to support alliance members with aerial patrols over Eastern Europe.

The French Navy chief of staff said in May that Russian warships shadowed US and French carriers in the Mediterranean at the start of the war. Vandier said that the Russian ships were a complex environment.

Tallis told Insider that the work being done for Project Neptune was a logical focal point for NATO alliance cohesion and signaling activities.

Tallis said that the project highlighted the value of mastering the complexity of rapidly shifting a large force package at an especially tense moment.