Block ships at Zeebrugge 22nd and 23rd of april (st.Georges day) 1918' blocking the entrance to the submarine base at Zeebrugge on the Belgium coast' the submarine campaign rose to its peak of success in 1917' when submarines sank 1,134 British ships with a tonnage of over 3,000,000' at one time' one in four of the British ships leaving port failed to return.
this picture shows the three old cruisers used as block ships' the first' the Thetis fouled a net and sank just outside the canal entrance, but the two following Intrepid and Iphigenia were sunk well in the canal entrance' also used the Vindictive and an old submarine was also used to be jammed between the piers and blown up to stop reinforcements reaching the mole. a simultaneous operation at Ostend was a failure as the attacking force could not find the harbour, the failure was however rectified in brilliant fashion the following month.