Complex sentence: The SS2 assault rifles are currently being pressed into service in the Indonesian military and police in order to gradually replace the SS1 assault rifles that are in service with the security forces from the 1990s.
Split into simpler sentences: The SS2 assault rifles are currently being pressed into service with the Indonesian military and police. They will gradually replace the SS1 assault rifles which have been in service with the security forces since the 1990s.