A former vice admiral of Japan's Maritime Self-Defense Force commented on the two MSDF helicopters that crashed during night-time training on Saturday.

Koda Yoji said he was greatly shocked by the accident. He said it's necessary to consider the possibility that there was a misunderstanding among the personnel or that they were not trained sufficiently.

He noted that the MSDF has had to respond to maritime activities by China and Russia, as well as patrol waters surrounding the Senkaku Islands in Okinawa Prefecture.

Japan controls the islands. The Japanese government maintains the islands are an inherent part of Japan's territory. China and Taiwan claim them.

Koda called on investigators to look into whether MSDF personnel have undergone training in line with safety regulations, in order to prevent another accident.

In regards to the submarine detection training that took place late at night, Koda said one combat strategy is to launch attacks when defenders are less capable, so enemy attacks could take place at any time.

He said submarine crews in particular could attack any time they want once they are underwater, so night-time training is especially important. The MSDF conducts anti-submarine training throughout the day.

Koda also commented on why the training took place off Torishima Island on the Izu Island chain, which is remote from the main island of Honshu. He said in the event of an emergency, US military reinforcements from the mainland would pass through near the island.

He added it makes sense that the MSDF trains in these waters as China and Russia would counter US forces there, and there is a likelihood submarines from these countries could enter the waters.