Correct

从军

/ cóngjūn /
Strokes

Definition

to enlist/to serve in the army

Example

As a Verb

join the army/ranks; go into the army; enlist (in the army); enter the service/army; become a soldier; join up; bear arms

1
Zhànzhēng
战争
bào
爆发
  
,
zhìyuàn
志愿
cóngjūn
从军
  

When war broke out, he volunteered for service in the army.