First, the successful bringing into the field of very large howitzers,
which, though they do lob their shells, lob them over a very great
distance. The Austrians have produced howitzers of from 11 to 12
inches in calibre, which, huge as they are, can be moved about in the
field and fired from any fairly steady ground; and the Germans have
probably produced (though I cannot find actual proof that they have
used them with effect) howitzers of more than 16 inches calibre, to be
moved, presumably, only upon rails. But 11-inch was quite enough to
change all the old conditions. It must be remembered that a gun varies
as the _cube_ of its calibre. A 12-inch piece is not twice as powerful
as a 6-inch. It is _eight times_ as powerful. The howitzer could now
fire from an immense distance. The circumference on which it worked
was very much larger; its opportunities for finding suitable steep
cover far greater. Its opportunities for moving, if it was endangered
by being spotted, were also far greater; and the chances of the gun in
the fortress knocking it out were enormously diminished.

Secondly, the high explosives of recent years, coupled with the vast
size of this new mobile howitzer shell, is capable, when the howitzer
shell strikes modern fortification, of doing grievous damage which,
repeated over several days, turns the fort into a mass of ruins.

Thirdly, the difficulty of accurate aiming over such distances and of
locating your hits so that they destroy the comparative small area of
the fort is got over by the use of aircraft, which fly above the fort,
note the hits, and signal the results.

Now, the Germans maintained that under these quite recently modified
conditions not even the best handled and heaviest gunned permanent