The underwater drills hold more weight this year, overshadowing the surface-level coordination seen in past exercises. For the U.S. and its allies across the Indo-Pacific, RIMPAC 2026 serves as serious preparation for potential conflict. In such a scenario, stealth and the element of surprise could prove just as vital as raw firepower. The focus on submarines reflects a growing recognition of the need to stay hidden and strike effectively in high-stakes operations.
Submarines and the shadow of the PLAN
RIMPAC 2026, which took place from June 24 to July 31, has shifted attention to undersea warfare. The increased number of submarines in the exercise this year—five in total, compared to just three in 2024—shows a change in military strategy. China’s growing carrier fleet, including the use of the Liaoning and the introduction of the J-35 aircraft, has prompted the U.S. and its allies to look to the ocean depths for tools that can survive hostile environments.
It is now clear that submarines are among the few assets that can threaten Chinese carrier groups without suffering the immediate losses that surface or aerial attacks typically involve. In the Indo-Pacific, where the PLAN has begun operating beyond the First Island Chain, the U.S. military is adjusting its approach to balance the use of land-based anti-ship missiles with the stealth advantages of undersea forces.
From Middle East battlefields to Pacific drillfields
The experiences gained by the U.S. military in the Middle East have now become part of the training for RIMPAC 2026. The rise of drone warfare and the use of low-cost, high-volume unmanned systems are no longer confined to that region. They are now a factor that naval forces in the Pacific must consider. Defense systems must now be ready for swarm tactics, which go beyond the traditional threats of missiles and fighter jets. Japan, Australia, and the Philippines are using RIMPAC to learn how their equipment works alongside U.S. military systems.
Sinking real ships for future conflicts
This year’s sinking exercises, or SINKEX, included the amphibious assault ship Peleliu and the Aegis cruiser Mobile Bay. These vessels are not just any targets; their size and role mirror those of the Type 075 and Type 055 ships currently in the Chinese navy. The exercise is as much about testing weapons as it is about preparing for real-world scenarios where these types of ships are active threats.
U.S. forces are using the SINKEX to evaluate the efficiency of their munitions, the coordination among their units, and the effectiveness of their command structures. The information gathered will help shape future procurement choices and tactical strategies. This exercise is a rehearsal for situations that the Pentagon may not openly admit it is preparing for, but one it must now be ready to face.