The North Atlantic Treaty Organization (NATO) Air Defender 23 exercise brings together 25 countries, led by Germany, according to The Wall Street Journal (WSJ) . Nearly 250 aircraft - including B-1 bombers, F-35 fighters and long-range unmanned aerial vehicles (UAVs) - will be deployed along with more than 10,000 troops from countries as far away as Japan, with about 2,000 flights expected to take place.

Lessons learned from the exercise will help NATO air forces better deploy in Europe and elsewhere to protect partners like South Korea and Japan.

The exercise comes as NATO’s status as a defence alliance has been upended after the Russia-Ukraine conflict erupted last year, leading to the biggest war in Europe since World War II. New East-West tensions are spreading globally, with joint Chinese and Russian exercises this week worrying US allies in Asia.

The US Air National Guard (ANG) will contribute 100 aircraft and 2,600 troops from 42 states. The exercise will stretch from the US to Germany to the Russian border in the Baltic region and around the Black Sea, from June 12 to 23.

By leading the exercise – first held in 2018 after Russia annexed Crimea four years earlier – Germany is seeking to raise its military profile. The conflict in Ukraine has convinced Berlin to reverse decades of de-emphasizing its armed forces.

“Germany needs to take more responsibility and sometimes take the lead among NATO countries in Europe… and we are demonstrating that we are capable of doing that in this exercise,” General Ingo Gerhartz, commander of the German Air Force, told the WSJ . “We want to say that this NATO territory is our red line,” he added.

The Air Defender exercise will practice the mass deployment of US military personnel and equipment to Europe to deal with various scenarios in which Russia attacks NATO members.

The main scenario involves the enemy capturing the German port of Rostock in an attack, which would trigger NATO's collective defense clause, known as Article 5. The response would include retaking the port and other infrastructure, as well as defending cities and going on the offensive.

Part of Germany's airspace will be closed to civilian flights for a short time. The exercise will also extend to NATO's eastern flank, over countries such as Lithuania and Romania, as well as Poland and the Czech Republic.

The air forces will also practice filling the gap in European security caused by the lack of air defense capabilities. They will simulate Russian missile and drone attacks and deploy fighter jets to counter them. Germany, Europe's most populous country, has 11 Patriot air defense systems, two of which are on loan to Poland and some are being maintained.