Complex sentence: The "Alizé" dwindled in numbers in the Indian Navy during the 1980s, was relegated to shore-based patrol in 1987, and was finally phased out in 1991, replaced in its duties by ASW helicopters.
Split into simpler sentences: The "Alizé" dwindled in numbers in the Indian Navy during the 1980s, was relegated to shore-based patrol in 1987. The type was finally phased out in 1991, replaced in its duties by ASW helicopters.