Complex sentence: When the Palestinian Liberation Organization (PLO) was founded in 1964, Nasser formally, but not practically, proclaimed that it would hold authority over Gaza, and a year later, conscription was instituted for the Palestinian Liberation Army.
Split into simpler sentences: When the Palestinian Liberation Organization (PLO) was founded in 1964, Nasser proclaimed that it would hold authority over Gaza, but that authority was never conferred in practice. A year later, conscription was instituted for the Palestinian Liberation Army.