ar,
introduced by Vice-Admiral Sir Henry Oliver, was of great help in
ensuring accuracy in laying minefields and consequently in reducing the
danger distance surrounding our own minefields.

As our mining operations increased in number we were driven farther and
farther out from the German ports for subsequent operations. This
naturally increased the area to be mined as the Heligoland Bight is
bell-mouthed in shape, but it had the advantage of making the operations
of German minesweepers and mine-bumpers more difficult and hazardous as
they had to work farther out, thus giving our light forces better
chances of catching them at work and engaging them. Such actions as that
on November 17, 1917, between our light forces and the German light
cruisers and minesweepers were the result. We did not, of course, lay
mines in either the Danish or Dutch territorial waters, and these waters
consequently afforded an exit for German vessels as our minefields
became most distant from German bases.

Broadly speaking, the policy was to lay mines so thoroughly in the
Heligoland Bight as to force enemy submarines and other vessels to make
their exits along the Danish or Dutch coasts in territorial waters.

At the end of the exit we stationed submarines to signal enemy movements
and to attack enemy vessels. We knew, of course, that the enemy would
sweep other channels for his ships, but as soon as we discovered the
position of these channels, which was not a very difficult matter, more
mines were laid at the end. In order to give neutrals fair warning,
certain areas which included the Heligoland Bight were proclaimed
dangerous. In this respect German and British methods may be contrasted:
We never laid a minefield which could possibly have been dangerous to
neutrals without issuing a warning stating that a certain area (which
included the minefield) was dangerous. The Germans never issued such a
warning unless the proclamation stating that half the Atlantic Ocean,
most of the North Sea, and nine-tenths of the Mediterranean were
dangerous could be considered as such. It was also intended, as mines
became available, to lay more deep minefields in positions near our own
coast in which enemy submarines were known to work; these minefields
would be safe for the passage of surface vessels, but our patrol craft
would force the submarines to dive into them. This system to a certain
extent had already been in use during 1915 and 1916.

Schemes