Military service for Korean male adults is a mandatory part of their responsibility towards their nation. Koreans take great pride in serving in the military. However, not all eligible men are always able to complete their military service. This could happen due to several reasons. However, none of them are pleasant in the least.
Kim Woo Bin went through a difficult period in his life when he was diagnosed with nasopharyngeal cancer and took a hiatus to recover from it. At the same time, he was supposed to enlist in the military, but he was exempted owing to his condition. Thankfully he's all better now and will be returning to acting soon.
Seo In Guk enlisted in the military but was exempted from completing his duty after a few days. This was because of an injury to his ankle. However, the actor faced a huge backlash from K-Netizens for allegedly trying to get out of the military. They believed that the military was biased towards celebrities without being understanding of Seo In Guk's dire condition.
Jo Jung Suk was granted an exemption from military service because, due to the passing of his father, he became the sole provider for his mother. He had to quit college and took on acting jobs to make ends meet. The military performed a financial audit on his family's situation and proceeded to exempt him from military service.
Yoo Ah In was exempted from military service because he was suffering from multiple injuries besides the persistent condition of his bone tumor. The military deemed him unfit for duty after multiple medical examinations. Thankfully, his agency revealed that he has been doing much better since then, and his tumor is also benign.