Turin one had to stand astride the road leading to that town; the
armies united at Dego would have covered Turin, because they would have
stood on the flank of the road leading to that town" (Napoleon).

(ii) _The position must not be too extensive_ for the troops at the
disposal of the commander, and this will be governed by the extent of
the line to be actually held. It will consist of a series of mutually
supporting tactical points, which can be held as "pivots on which to
hinge the defence of the position," and the object must be to obtain
the maximum of fire effect on all ground over which the enemy can
advance with the minimum of exposure to his fire. A rough-and-ready
rule is that unless one rifle per yard of the frontage occupied can be
supplied by the "troops to hold the position" (which should not exceed
one-half the available force) then the position is too extensive and
should be narrowed. On the other hand, too narrow a front may enable
the enemy to develop, early in the engagement, strong flank attacks,
which may make the position untenable before the time is ripe for the
assumption of the offensive. The _Conde-Mons-Binche_ line held on
August 22-23, 1914, by Sir J. French's army (I. Corps, General Sir D.
Haig; II. Corps, General Sir H. L. Smith-Dorrien) had a total width of
25 miles, and the troops at disposal, including General Sir E. H. H.
Allenby's Cavalry Division, consisted of about 75,000 all arms. The
frontage actually held did not exhaust half this force at the rate of
one rifle per yard, and a position in rear had also been selected,
between Jerlain and Maubeuge, with a frontage of 15 miles. The
_Retreat from Mons_ was {88} due not to the excessive width of
frontage, but to the success of the German attack on the French V.
Corps at Charleroi (August 23, 1914), which left the right flank of the
British Army "in the air," while two German Corps were working round
the left flank. The British III. Corps (General Sir W. P. Pulteney)
did not arrive until the retreat was in full swing. At the _First
Battle of Ypres_ (October 31, 1914) many parts of the line were held
with one rifle for 17 yards, and there were no Supports or Local or
General Reserves. Yet the line was not only maintained but a
counter-attack at Gheluvelt thrust the attacking Germans behind their
entrenchments.

(iii) _There must be a clear field of fire_ to prevent the enemy
approaching unmolested within effective range, and