I've read some things about how Korean American males 18 or older can't visit South Korea between the age of 18 and 35? 38? (inclusive?) without being drafted into the military. South Korea, of course, requires all able male South Korean citizens between the ages of 18 and 28? 35? to serve in the military for 18? 24? months. Wikipedia's article on South Korean nationality law says that one way to automatically acquire South Korean nationality is “By being born to either a South Korean national father or South Korean national mother after 13 June 1998, or to a South Korean national father before then.” Does this require any registration on the part of your parents/relatives, or is it truly automatic?

An article by Seattle Pi from 2004 gives an example of someone who was drafted because “it appears a family member -- maybe his paternal grandfather or his father, who is divorced from Chun's mother and lives in South Korea -- entered his name in the nation's family census registry, the hojok.” However, according to the Wikipedia article on hoju, it was abolished on January 1, 2008.

It seems that before 2010, South Korean dual citizenship was impossible, so if one were born before 2010 and had ethnically Korean parents who were both American citizens at the time of their birth, that child wouldn't have any chance of automatically being a South Korean citizen?

Is it still true that one would have to rescind their South Korean nationality before the age of 18, and one is unable to do so later?

Does visiting Korea for a short period of time (I've heard 30 days) eliminate the risk of being drafted? Is there any paperwork you can fill out beforehand like you can with Israel?

The relevant laws have been changing quite a bit in the past few decades apparently, so it's hard to tell what information is still true or what's outdated. Please cite reliable sources if you can.

For clarification, I am not in any way Korean, so this question is just out of curiosity and/or for a friend.