Complex sentence: Palestine (the southern zone) was reserved for the British, and on 8 October, French troops disembarked in Beirut and occupied all the Lebanese coastal region until Naqoura (the western zone) replacing British troops there.
Split into simpler sentences: Palestine (the southern zone) was reserved for the British. On 8 October, French troops disembarked in Beirut and occupied the Lebanese coastal region south to Naqoura (the western zone), replacing British troops there.