Complex sentence: Indonesia, then firmly-rooted in the anti-Soviet camp in Southeast Asia, was alarmed by the left-leaning parties that looked set to win that election and eager to expand its territory, invaded the territory in 1975 and annexed East Timor the following year.
Split into simpler sentences: Indonesia, then firmly-rooted in the anti-Soviet camp in Southeast Asia, was alarmed by the left-leaning parties that looked set to win that election. Indonesian invaded the territory in 1975 and annexed East Timor the following year.