brows or gangways
for landing forces, had been brought up 25 minutes earlier--to
be exact, at a minute past midnight--along the outer side of the
high mole or breakwater enclosing the harbor. Here, in spite of a
heavy swell and tide, she was held in position by the ex-ferryboat
_Daffodill_, while some 300 or 400 bluejackets and marines swarmed
ashore under a violent fire from batteries and machine guns and
did considerable injury to the works on the mole. Fifteen minutes
later, an old British submarine was run into a viaduct connecting
the mole with the shore and there blown up, breaking a big gap in
the viaduct. Strange to say, the _Vindictive_ and her auxiliaries,
after lying more than an hour in this dangerous position, succeeded
in taking aboard all survivors from the landing party and getting
safely away. Motor launches also rescued the crews of the blockships
and the men--all of them wounded--from the submarine. One British
destroyer and two motor boats were sunk, and the casualties were
176 killed, 412 wounded, and 49 missing. For a considerable period
thereafter, all the larger German torpedo craft remained cooped
up at Bruges, and the Zeebrugge blockships still obstructed the
channel at the end of the war.

[Illustration: ZEEBRUGGE HARBOR WITH GERMAN DEFENSES AND BRITISH
BLOCKSHIPS]

_The Convoy System_

Of all the anti-submarine measures employed, prior to the North
Sea Barrage and the Zeebrugge attack, the adoption of the convoy
system was undoubtedly the most effective in checking the loss
of tonnage at the height of the submarine campaign. Familiar as
a means of commerce protection in previous naval wars, the late
adoption of the convoy system in the World War occasioned very
general surprise. It was felt by naval authorities, however, that
great delay would be incurred in assembling vessels, and in restricting
the speed of all ships of a convoy to that of the slowest unit.
Merchant captains believed themselves unequal to the task of keeping
station at night in close order, with all lights out and frequent
changes of course, and they thought that the resultant injuries
would be almost as great as from submarines. Furthermore, so long
as a large number of neutral vessels were at sea, it appeared a
very doubtful expedient to segregate merchant vessels of belligerent
nationality and thus distinguish them as legitimate prey.

[Illustration: BRITISH, ALLIED AND NEUTRAL MERCHANT SHIPS DESTROYED
BY GERMAN R