Here is an article that explains a challenge that all male Korean college students have to deal with, when to do your mandatory service:
Mr. Oh, a 24-year-old college student, wanted to serve his mandatory military service sometime between January and March of 2013. Aware that he would have to return to school upon his completion of duty, he wanted to hit the books straight away, making no time for staying idle.
In Korea’s current draft system, Oh needed to be wise about which month he starts and ends his service. In the best-case scenario, he could return to school right after getting discharged from the military. In the worst-case scenario, he would have to wait for an entire semester.
In the end, it didn’t work out for Oh. The competition was high. Way too many men had the same thoughts as him and the lucky-draw didn’t play out to his advantage.
Oh eventually began in June 2013, one of the least-expected – and most unpopular – month of the entire year.
He was discharged in March 2015, after the spring semester began. [Joong Ang Ilbo]
You can read more at the link, but this is just another example of why I have a lot of respect for the Koreans that complete their mandatory military service.