Correct

袭其不意

/ xí qí bùyì / 
Strokes

Example

Definition

attack sb unawares; strike sb off guard

1
Gōngjī
攻击
dífāng
敌方
shí
时
  
,
bìxū
必须
xí
袭
qí
其
bùyì
不意
  
,
cái
才
néng
能
qǔshèng
取胜
  
。

We can't win unless we attack the enemy off guard.