During World War I, Greece did not enter the war on the side of the Triple Entente until 1917 and, due to Greece's neutrality the four Niki-class ships had been seized by the Allies in October 1916, taken over by the French in November and served in the French Navy from 1917 to 1918.
The passage describes how Greece's neutrality during World War I led to the seizure of four Niki-class ships, which were then taken over by the French and used in their navy.