Complex sentence: Before the 1970s, the only means of transportation to and from the islands were by hiring fishers' boats, and even then only Woody Island was accessible, while the rest of the Paracels, the Zhongsha Islands and the Spratlys were only accessible to military personnel.
Split into simpler sentences: Before the 1970s, the only means of transport to and from the islands was by fishing boat, and even then, only Woody Island was accessible. The rest of the Paracels, the Zhongsha Islands and the Spratlys were only accessible to military personnel.