Complex sentence: Walters has made at least one visit to Pakistan and possibly to Afghanistan where it is alleged he has received training at a terrorist training camp, and in 2003, Walters wrote a farewell letter to his mother.
Split into simpler sentences: Walters has made at least one visit to Pakistan and possibly to Afghanistan where it is alleged he has received training at a terrorist training camp. In 2003, Walters wrote a farewell letter to his mother.