Taiwan on Monday, for the first time during its annual drills, reduced mobile internet speed across a large part of the center of the island in order to simulate communication disruption in the event of a Chinese attack or a natural disaster.

During the drills, focused on the major city of Taichung on Monday, only basic mobile phone services were operating. ATMs, traffic lights, landline phones, and fixed internet were not affected.

The government simultaneously sent text messages in Chinese and English and informed mobile phone users about “simulated air attacks on communications infrastructure.”

The government had previously announced details of the drills broadly.

Taiwan, which China considers part of its territory, has lived for years with threats of an attack from that country.