Complex sentence: It is believed that under President Slobodan Milosevic, Serbia had a very close relationship with North Korea and had bought North Korean weapons and it was rumoured that North Korean students came to study in Belgrade.
Split into simpler sentences: It is believed that under President Slobodan Milosevic, Serbia had a very close relationship with North Korea and had bought North Korean weapons. It was rumoured that North Korean students came to study in Belgrade.