4. A few guns (called "safety armament") should be in the forts, and
these must be protected by armour.
5. The bulk of the artillery of the defence should be outside the
forts; the direct-fire guns preferably in cupolas, the howitzers in
concealed positions.
6. The forts should be connected by lines of entrenched infantry
positions and obstacles, permanent bomb-proof shelters being provided
for the infantry.
7. There should be ample communications--radial and
peripheral--between the place and the forts, both by road and rail.
8. Special lines of communication--such as mountain passes--should be
closed by barrier forts.
These considerations will now be taken somewhat more in detail, but
first it will be useful to deal with the plan of Metz in 1899 (fig. 44).
Metz.
Here the fortifications of successive periods can be readily
recognized. First the old enceinte, unaltered by the Germans and now
_declassee_. Next the detached forts, begun by the French engineers in
1868 and still unfinished in 1870, can be readily recognized by their
bastioned trace. Among them are Fort Manteuffel, formerly St Julien,
and Fort Goeben (fig. 45), formerly Queuleu. These were not altered in
their general lines.
[Illustration: From Plessix and Legrand's _Manuel complet de la
fortification_, by permission.