U.S. and Japan navies launch ANNUALEX 2025 in Philippine Sea to train in maritime warfare.

Japan’s Maritime Self-Defense Force and U.S. naval forces began ANNUALEX 2025 on 20 October in the sea and airspace around Japan, joined by Australia, Canada, France, New Zealand, and U.S. Marines. The exercise sharpens combined air defense, anti-submarine warfare, and logistics that underpin sustained presence and crisis response in the Indo-Pacific.

Japan’s Maritime Self-Defense Force, the U.S. Navy, and the U.S. Marine Corps began ANNUALEX 2025 in the Philippine Sea on 20 October 2025, a multilateral exercise focused on maritime communications, anti-submarine and air warfare, and replenishment at sea, with JS Kaga (DDH 184) leading the JMSDF contribution and U.S. assets including USS Shoup, USS Robert Smalls, P-8A Poseidon, a submarine, logistics ships, and F-35B aircraft from VMFA-242; Australia, Canada, France, and New Zealand are also participating.
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JMSDF with the U.S. Navy and Marine Corps plus Australian Canadian and French navies conduct ANNUALEX 2025 in the Philippine Sea on Oct. 20 2025 showcasing allied interoperability for a free and open Indo Pacific. (Picture source: US DoD)

On the surface side, the U.S. Navy is deploying the Arleigh Burke-class destroyer USS Shoup (DDG 86) and the Ticonderoga-class cruiser USS Robert Smalls (CG 62). P-8A Poseidon aircraft extend surveillance well beyond the horizon, while the logistics backbone consists of Lewis and Clark-class dry cargo ships USNS Amelia Earhart (T-AKE 6) and USNS Wally Schirra (T-AKE 8), plus the fleet oiler USNS Tippecanoe (T-AO 199). A U.S. attack submarine adds a discreet undersea element. On the Japanese side, JS Kaga leads the activity, integrating air-surface options and anti-submarine warfare with partner navies.

In capability terms, a few technical aspects stand out. First, Robert Smalls and Shoup, fitted with the Aegis combat system and SPY-1 phased-array radars, employ versatile vertical launch systems that enable area air defense, missile tracking, and rapid mission reconfiguration from the same cells. Second, the P-8A, equipped with the AN/APY-10 radar, advanced sonobuoy processing, and the ability to employ the Mk 54 lightweight torpedo, turns wide ocean areas into searchable grids rather than unknowns. Third, the F-35B, with short takeoff/vertical landing and sensor fusion, enables handoffs between sea and air, which shortens engagement timelines in congested waters.

At the center of the formation, Kaga concentrates command and anti-submarine functions. As an Izumo-class ship, it fields a full-length flight deck for sustained helicopter operations supporting dipping sonars and prosecutions. Its command facilities streamline airspace deconfliction, surface track management, and submarine contact handling within a busy multinational picture. In a multi-ship environment, this coordination function can be as valuable as any individual weapons fit.

ANNUALEX trains three main pillars: communication discipline, layered defense, and endurance. Communication drills go beyond radio phraseology; they test datalink integrity, emissions control, and the ability to maintain a common operational picture when nodes are deliberately stressed. Layered defense combines Aegis area coverage with point defenses and combat air patrols, while ASW units establish barriers, conduct active and passive searches, and practice rapid localization when a contact of interest appears. Endurance comes from the underway replenishment cycle. Dry cargo ships and oilers keep the formation on station without pier support, a prerequisite for sea control in a theater defined by long distances.

The force mix reflects an approach consistent with distributed maritime operations. A submarine conducts reconnaissance and sea denial. P-8As survey, classify, and develop tracks, then hand them to surface or air units best placed to intercept. Surface ships maintain air-defense umbrellas and hold long-range fires, while logistics vessels move under protection to refuel and resupply. When VMFA-242’s F-35Bs enter the cycle, they bridge the shore-sea seam, contribute to air control, and pass targeting data using sensor fusion, including under restricted radio conditions.

The previous edition, ANNUALEX 2023, relied on Carrier Strike Group One centered on USS Carl Vinson. The 2025 configuration differs, yet the throughline remains: set habits, validate TTPs, and ensure combined crews can fall into the same rhythm without prior notice. Participation by Australia, Canada, France, and New Zealand adds complexity. National procedures differ at the margins, but the exercise drives convergence where it matters, including safety rules for replenishment, flight-deck operations, and submarine-aircraft coordination.

The Philippine Sea sits at the junction of Northeast and Southeast Asia, near contested air and maritime approaches and within reach of actors that shape Indo-Pacific stability. A credible allied ASW posture addresses navies investing in quieter submarines. A resilient, layered air-defense construct addresses those experimenting with massed missiles and uncrewed systems. The logistics choreography indicates an intention to sustain presence rather than conduct brief port calls. The aim is to keep escalation ladders short by demonstrating that combined forces can detect, track, and, if required, fight as one. In that sense, ANNUALEX 2025 is both routine and consequential, another stitch in an allied fabric designed to keep the region open, predictable, and resistant to intimidation.