Eight decades ago they faced each other on the battlefields of the Pacific during World War II. Today, the United States and Japan are close military partners, and they have just demonstrated it with one of the largest joint maneuvers in their recent history: on October 19 they began the Keen Sword 2027 exercise, which mobilizes tens of thousands of personnel and even a nuclear aircraft carrier. The United States and Japan launched Keen Sword 2027: what this alliance is about Keen Sword is a bilateral military exercise between the United States and Japan that is held every two years. The edition that has just begun, identified as Keen Sword 27, is the eighteenth since the series began in 1985, and it takes place between October 19 and 29, 2026, over eleven days. The opening ceremony took place on Ishigaki Island, the westernmost point of Japanese territory. Around 56,000 personnel in total are taking part: about 45,000 from Japan’s Self-Defense Forces (JSDF) and about 11,000 U.S. military personnel. According to the official statement from Japan’s Joint Staff, on Japan’s side there are also about 6,100 vehicles, 40 ships and 260 aircraft. The most striking piece of the operation is naval: the nuclear aircraft carrier USS Theodore Roosevelt (CVN-71), which leads Carrier Strike Group 9 (CSG-9), arrived at Yokosuka Naval Base together with the guided-missile cruiser USS Chosin (CG-65). What is being tested The exercise aims to improve coordination between the two forces in different crisis scenarios. Planned activities include maritime operations, air and missile defense, facility protection and repair, logistics and resupply, and casualty evacuation. The underlying goal is to improve interoperability, information sharing and defensive coordination between the two countries. In fact, the logistics component and readiness to operate together in the future are a central part of what is being tested. In what context this joint military exercise is taking place The maneuvers come at a time of regional tension. According to international agencies, the exercise is taking place amid friction between China and Japan over Taiwan and in the face of Beijing’s growing military and economic influence in Asia-Pacific. Neither the United States nor Japan officially said the maneuvers are aimed against China; the official messages pointed to shared values, crisis response and deterrence. At the same time, it was reported that U.S. Marines are deploying anti-ship and air-defense systems on the southwestern Japanese islands, near Taiwan.