Complex sentence: A large project of Geiger's was the Three Letter Campaign as Geiger advised each member of the legion to write there letter, one to their congressman and one to each senator, to improve the GI Bill for veterans of Vietnam.
Split into simpler sentences: A large project of Geiger's was the Three Letter Campaign as Geiger advised each member of the legion to write three letters: one to their congressman and one to each senator. The purpose of the campaign was to improve the GI Bill for veterans of Vietnam.