3 
The second or retired line can only be fixed when the besieger has made clear 
which face of the fortress he means to attack. 
This line should form a chord to the face of the main line under attack and 
should extend between two permanent forts in that line not themselves under 
attack but on the flanks of the attacked are—the defences of this line should be 
similar to those in the main line but necessarily of a slighter and more temporary 
type. Field-works erected on prominent points would take the place of the per- 
manent forts in the main line. Possible positions for such work should be fixed 
in time of peace and the size and character of the works decided on, the functions 
of this second line are to provide for the continuity of the defence even after any 
particular section of the main line has been pierced or rendered untenable to pre- 
vent a successful attack on the main line being immediately followed by the fall 
of the place and to facilitate the withdrawal of troops and materiel. 
The functions of the forts of the main line are to command by the fire of long 
range guns the country over which the besieging army must manoeuvre to attack 
the defensive position ; to support the mobile army in the defence of that posi- 
tion; to provide these guns with efficient defences which can only be rendered 
untenable by a deliberate bombardment from comparatively short ranges, and to 
afford such flanking protection to the intervals that these would be secure from 
assault till more than one of the forts had been silenced. 
T].—DEFENCE. 
Armament.—A greater diversity of types and calibres is admissible and even 
necessary in the armament of a fortress than in that of a siege-train. And the 
armament of a Ist class fortress should include the following types : 
(1.) A few long range guns to act against the investing columns at a distance, 
to oblige the assailant to place his park or depdt at a maximum distance, to render 
the task of arming the siege batteries and the supply of ammunition arduous and 
perilous, and to give material support to the mobile portion of the garrison in 
their defensive battle and during the other preliminary operations. 
Long range can only be obtained at the expense of lightness and mobility, but 
as these considerations are not in all cases so essential for the defence as for the 
attack the former would surrender an important advantage if it did not include 
some long range guns in its armament. ‘These guns should be invariably placed 
in the forts of the main line, they will act by direct fire and should be aimed by 
direct visual laying. They should if possible command all the “ terrain ” included 
in their ares of fire which should be as large as possible—-should be placed behind 
defences proof against high explosive shells—and their magazines and shelters 
should be similarly protected. 
(2.) The remainder of the armament need not be superior in calibre to that 
advocated for siege-trains. As the bulk of the armament should be distributed in 
the intervals between the forts, mobility becomes a desideratum, and as the defences 
of siege batteries must necessarily be slight, powerful guns are unnecessary, 
howitzers of about 5:8” calibre and medium mortars! are recommended as most 
suitable for indirect or curved fire, the destruction of overhead cover, &e. 
(3.) The flanking of the batteries and trenches in the intervals and the im- 
mediate defence of the forts themselves should be secured as far as possible by 
light and quick-firimg guns on disappearing mountings in the forts—these guns 
should have a command over the “ terrain’ in the immediate vicinity of the forts 
and over the intervals between themselves and the neighbouring forts on either 
flank, 
(4.) In addition to the above there should bea proportion of light mobile 
guns and howitzers of about 3:5" calibre. apidity of fire is absolutely essential 
1 By mortars are meant rifled howitzers mounted at fixed angles of elevation. 
