Japan said Tuesday that they will double the Mitsubishi made F-15J fighter squadron in Okinawa prefecture because Chinese forces already increased their presence in that area.

According to Japan’s Air Self-Defense Force (JASDF), the deployment in Naha Air Base will be finished by February and it will have 40 additional F-15J jets.

The decision follows an increased number of “scrambles”, or emergency takeoffs, from Naha in 2015, which came largely in response to approaching Chinese aircraft.

Last year, 441 JASDF jets were combined from Naha, which is more than double the number of combined jets in 2011.

The plan to boost the squadron is the latest effort of JASDF to strengthen Japan’s defense of the disputed Senkaku islands, or Diaoyu islands as they are known in China.

The Mitsubishi F-15J/DJ Eagle is a twin-engine, all-weather air superiority fighter based on the McDonnell Douglas F-15 Eagle. The Japan Air Self-Defense Force had 201 F-15J/DJs in use as of 2015. Japan has a total of 223 active units of this aircraft.