摇旗信号

例句：

1. 1.The army used flags to communicate with each other during battles.
   军队在战斗中使用旗帜进行通信。
2. 2.The captain raised his flag to signal the start of the attack.
   队长挥动旗帜以示意开始进攻。
3. 3. The sailors followed the flag wave to find their way back to the ship.
   水手们跟随旗帜的挥动找到返回船只的路。