INFINITE's Sungjong has become the fourth member of his group to begin their mandatory military service.

Sungjong left a handwritten letter to fans earlier today announcing his enlistment through his Instagram account. 

The letter states,

"To Inspirit,

Hello Inspirits

This is INFINITE's youngest member, Sungjong.

It's been a while since I've written a letter to you all. I've been thinking a lot before I started writing this, but I wanted to be the first to let our fans know, so I writing this to you now.

By the time you read this letter, I will already be enlisted in the military.

I'm sorry I didn't tell you in advance, I'm sorry and I'm sorry again :(

It would have been good to be able to see your faces before I left.

I'll at least show you my face from the different activities I did beforehand as a way to say goodbye.

I'll be back after a good and healthy military life.

Our Inspirits can wait for me for just a little while, right?

 I'll come back as a strong and cool Sungjong.

I love you Inspirit.

I miss you Inspirit.

Don't forget Sungjong. Inspirit..."

Sungjong enlisted on July 22nd to begin his basic military training. Upon completion, he will serve as a public service worker.