There have been large-scale military manoeuvres on the frontier.

边境地区曾有过大规模的习。

This happened in the center of operations.

生在习的过程中。

The fleet is maneuvring off the east coast.

舰队正在东海外习。

The fleet is -ring off the east coast.

舰队驶离东海进行习。

The drilling troops mustered on the hill.

习部队在小山上集合起来了。

Military planes flew over the country in a warlike action.

用飞机在进行习时从该国上空飞过。