Complex sentence: Although Thao's last plot failed, his activities in 1965 and the resultant infighting led to a series of internal purges within the ARVN, and amid the instability, the Vietcong made strong gains across the country throughout the year.
Split into simpler sentences: Although Thao's last plot failed, his activities in 1965 and the resultant infighting led to a series of internal purges within the ARVN. Amid the instability, the Vietcong made strong gains across the country throughout the year.