Complex sentence: Pollard claimed that he provided only information that he believed was vital to Israeli security and that was being withheld by the Pentagon, in violation of a 1983 Memorandum of Understanding between the two countries regarding the sharing of vital security intelligence.
Split into simpler sentences: Pollard claimed that he provided only information that was vital to Israeli security and that it was being withheld by the Pentagon, in violation of a 1983 Memorandum of Understanding between the two countries. The Memorandum of Understanding was an agreement between the United States and Israel regarding the sharing of vital security intelligence.