Found this.... gives is an idea of Korean military mandatory service and, YSH going in at age 19 years.
cr: bibibelle tumblr....
All Korean males, ages 18 to 35, must serve two years of mandatory military duty. Many actors must fulfill this duty at the height of their career. This can mean they face tough competition from younger actors who have become big names while they are gone.
Two k-drama actors will finish their military duty this year and are already looking for their first comeback project.
Both Yoo Seung Ho and Lee Je Hoon enlisted in 2012 and are almost done with their mandatory service.Lee Je Hoon will be done this month and Yoo Seung Ho will be discharged in December. Lee Je Hoon has already chosen his comeback project.
Many actors choose to wait until they are around 30 so they can act in as many dramas as possible while they are still in their 20s. Two years is a long time to be out of commission when you are an actor.
Yoo Seung Ho was an exception to that rule. He enlisted at the age of 19, shortly after playing the controlling Kang Hyung Joon in the popular drama “Missing You.” He also rejected any publicity surrounding his enlistment and after finishing basic training served in an assistant instructor position in the 27th District Recruit Training Center. He has not yet chosen a comeback role but is considering offers.