Premise: SEOUL, Oct 24 (Reuters) - South Korea, the United States and Japan started a two-day missile tracking drill on Tuesday, South Korea's military said, in preparation for any missile or nuclear threats from North Korea. The exercises will be held in waters off the coasts of South Korea and Japan, the South Korean military said in a statement. The drills have been taking place every few months following an agreement made during a Security Consultative Meeting between South Korea and the United States last year. (Reporting by Christine Kim; Editing by Paul Tait)
Hypothesis: The drills have taken place no more than twice.