Complex sentence: The anti-religious campaign of Frelimo formally ended in 1982 when the party in power held a big meeting with all the main religious institutions where it claimed mistakes had been made and national unity needed to prevail.
Split into simpler sentences: The anti-religious campaign of Frelimo formally ended in 1982 when the party in power held a big meeting with all the main religious institutions. On that occasion, it claimed mistakes had been made and national unity needed to prevail.