sentences:  They were supported by three transport ships namely the "T673", "T674" and "T675" along with 60 experienced sailors and technicians from the 125th Naval Transport Brigade.The North Vietnamese operation would commence at 12.00 am on April 9, 1975, to coincide with the North Vietnamese ground attack on Xuân Lộc and to take advantage of low tide to land the special forces on the South Vietnamese-occupied sections of the Spratly Islands.To maintain the secrecy of their operation, the North Vietnamese Navy kept their radio communications to a minimum in the days leading up to the attack.