Special Report: Japan US, sharpen archipelagic defence concepts at ‘Keen Sword 27'

A TPS-80 radar unit being loaded onto a Japan Air Self-Defense Force C-2 aircraft during Exercise ‘Keen Sword 27'. (US Department of War)

Exercise ‘Keen Sword 27' (KS27) took place from 19 to 29 October 2026 at locations across Japan and in surrounding sea and airspace. It was the 18th field-training iteration of the US-Japan exercise, which began in 1985 and generally alternates field and command-post exercises.

Japan's Joint Staff put Japanese participation at about 45,000 personnel, 6,100 vehicles, 40 vessels, and 260 aircraft, while US participation was at approximately 12,000 personnel.

Dispersed strike

One notable deployment during KS27 took the Type 25 missile outside its Kengun garrison for the first time.

The Japan Ministry of Defense (MoD) designated the ground-launched version of the upgraded Type 12 surface-to-ship missile (SSM) as the Type 25 SSM on 31 March 2026 and based it at Camp Kengun in Kumamoto Prefecture. When the exercise began, the system had been based there for about seven months.

Before the exercise, a Joint Staff spokesman said the Type 25 would deploy outside Kengun for the first time, without being fired.

The launchers were subsequently deployed at the Onobaru Maneuver Area in Nagasaki Prefecture for anti-ship training.

JGSDF chief General Masayoshi Arai confirmed the deployment at a press briefing 20 October. The objective of the drills was to practise deployment, confirm firing procedures, and work out how to protect the launchers away from base, he said.

“Our country is facing the most severe and complex security environment since the war, and it is urgent to quickly build stand-off defence capabilities capable of deterring invading ships and landing forces,” Gen Arai said.