袭击，发生在被袭击者并不知情的情况下，更突然，攻击，则是两个人正面的发生。

ambush 襲擊 attack 攻擊 you can see how they are different in English

攻擊 is probably same as 襲擊. Their biggest difference is, 攻擊 means attack only, however, 襲擊 means attack someone but he don't know you are going to attack him. 攻擊 is the most basically way to talk about attack. In literary writing, we would use more words which means attack in the other way, such as 襲擊, 砲擊 (attack sb with firing or bombs), 奇襲 (which means 襲擊 but more suddenly and specially). Hope I can help you:)

攻击 attack, assault 袭击 raid, assault