Your troops in the base will fight enemy automatically when enemy is approaching(on condition that you have checked "auto dispatch" box). You can dispatch a large part of your troops in the base to garrison.

您基地里的部队在敌人接近的情况下（前提是要在基地中开启该功能）自动出击。您可以在基地中派驻部队来防守。

Buying city protection is a more effective way to defend your city, which allows you to spend diamond to protect your city for a period of time. Buildings in Admin Area will not be attacked during city protection time (troops can fight and be attacked as usual).

购买城市保护更有助于保护您的城市，您需要用钻石购买来获得一定时间的保护。保护期间城市所有建筑都将得到保护（但是部队依旧可以反击）。