From information received, it would appear that three flotillas had been ordered to bombard Dunkirk, La Panne, and Bray Dunes. One of the British ships was slightly damaged, and returned to port. On the French side there were neither killed nor wounded.
British boats, belonging to the Grand Fleet, made an excursion into the Kattegat, the strait between Sweden and Denmark, on April 15, 1918, sinking 10 German trawlers and returning without having suffered any casualties.
British light forces operating in the Helgoland Bight on April 20, 1918, obtained touch with German light forces, who retired behind mine fields. A few shots were exchanged at extreme range and one German destroyer was observed to have been hit.
Early in the morning of April 23, 1918, British naval forces made a successful attack against Ostend and Zeebrugge, both of them important German submarine bases. The raid was undertaken under the command of Vice Admiral Roger Keyes, commanding at Dover French destroyers cooperating with the British forces. There were six obsolete cruisers which took part in the attack—Brilliant, Sirius, Intrepid, Iphigenia, Thetis, and Vindictive. The first five were filled with concrete, and were to be sunk in the channels and entrances to the ports if that could possibly be managed. Vindictive, working with two auxiliary craft, ferryboats well known on the Mersey, Daffodil and Iris, carried storming and demolition parties to the head of the mole at Zeebrugge. Vindictive was specially fitted with brows for landing the storming parties and armed specially for the operation with batteries of Stokes mortars, flame throwers, &c. The men employed on the blockships and in the storming and demolition parties were bluejackets and Royal Marines, picked from a very large number of volunteers from the Grand Fleet.
There were light covering forces belonging to the Dover command, and Harwich forces, under Admiral Tyrwhitt, covered the operation in the north.
A force of monitors, together with a large number of motor launches, coastal motor boats, which, as is known, are small, fast craft, carrying a minimum crew of six, and other small craft took part in the operation.
It was a particularly intricate operation, which had to be worked strictly to time-table and involved very delicate navigation on a hostile coast without lights and largely under unknown navigational conditions, which have developed since the war, with the added danger of unknown mine fields. One of the essentials to success was a high development of the scientific use of smoke or fog—it is more fog than smoke—for which certain conditions of force and direction of wind were necessary, so as to protect the operation from batteries which could have flanked it.
The general plan of operation was as follows:—After an hour of intense bombardment of Zeebrugge by the monitors, Vindictive, with the auxiliaries Iris and Daffodil, were to run alongside the head of the mole, attacking with gunfire as they approached; storming parties and demolition parties were to be landed. Meantime three blockships, assisted by the coastal motor boats and launches, were to make for the entrance to the canal and to be run aground and blown up. Two old and valueless submarines were to run against the pile work connecting the masonry portion of the mole with the shore, and, being filled with explosives, were to be blown up, destroying the pile-work connection.
