"Plan 17," issued to commanders-designate of armies and
their chief-of-staff in Feb. 1914, was based on certain assump-
tions which may be summarized as follows: On the right wing,
the hypothesis of a German invasion through Switzerland was
assumed to be so improbable that only an echelon of three re-
serve divisions, and these available for active operations towards
Belfort, was allotted to that flank. On the left flank, the prob-
lem was far more delicate and difficult, as it depended on whether
or not Belgian neutrality would be violated, and, if so, how far
N. the right of the German forces would extend. It was involved
with two other questions, that of the attitude of Belgium and
that of the strength of the German army; neither of these was an-
swered very definitely, and the assumptions of the plan proved
substantially incorrect. Belgian aid was not counted upon
indeed, in one important detail provision was made for the case
of the Belgians not interfering with a German march-through
and the German army for battle purposes was assumed to con-
tain only some 20 or 21 active corps, the reserve divisions, it was
thought, not being available till after an interval, and then only
for subsidiary functions such as sieges and railway guarding.
The conclusion drawn was that the German right, in case Belgian
territory was taken in, would extend to the limit of the Ardennes
i.e. the Belgian Meuse at the farthest, if as far. But the
hypothesis of a frontal attempt of the Germans to break through
between Longwy and the Vosges, without touching Belgian
territory, was the basis of the plan; and the measures to be taken
in case Luxemburg and the Belgian Ardennes came into the
theatre of war were embodied in a "variant." It was supposed,
in addition, that attempts might be made by the Germans in
Lorraine or the Woevre to break into the French concentration
areas in the first days of hostilities; and a very strong protective
system (drawn back in the Woevre out of range of a sortie from
the Metz outer defences) was provided against this emergency,
the augmentations of the peace effectives brought about by the
" Three Years Law " having made this possible. On to this pro-
tective system, constituted by one corps of each front-line army,
the remaining corps were to graft themselves as they arrived,
and the whole was to be ready for active operations on the
1 2th day of mobilization. It was assumed correctly that the
Germans would attack, and incorrectly that their attack
would be a simultaneous onset of fairly evenly distributed
forces; and it was argued that a French offensive, debouching
with startling rapidity, would create a situation with which the
German military system was not elastic enough to deal.
These active operations, if Belgian territory remained un- touched, were to be a general offensive of four armies with another immediately behind them, directed eastward from the Meuse below Verdun and northeastward from the Nancy- Vosges front, northward from Belfort; and, if Luxemburg and Belgium were infringed, an equally general offensive with all five armies in line, those of Alsace and Lorraine directed as before, but those of the Woevre and the middle Meuse northeastward and even northward according to the positions found to be occupied by the German right. In either case the central army, besides helping its neighbours as required, was to drive back all sorties from Metz and begin the investment of that place.
The dispositions of the plan were as follows: The /. Army (five corps, two cavalry divisions and army artillery) was to attack with its main body from the concentration area west of the Vosges in the direction Baccarat-Saarburg-Saargemund; the right, VII. Corps and a cavalry division based on Belfort, to advance into upper Alsace, rouse the population to a revolt, and hold as large a German force engaged as possible; between the VII. Corps and the main body, a smaller force in the Vosges was to maintain liaison and by descents into Alsace to cooperate with the advance from Belfort.
The //. Army (five corps, two cavalry divisions and army artillery), grouped initially about Nancy and Luneville, on the left of the I., was to attack in the direction Chateau Salins- Saarbrucken. The improvised fortifications of Nancy in the first stage, -and a group of reserve divisions issuing therefrom in the later stages, were to protect the left of this army against Metz;
and the I. Army, developing its advance along the Vosges, was to guard the right, cooperating in the battle of the II. Army with all the forces not absorbed by the flank along the Vosges. !
The ///. Army (three corps, three reserve divisions, one cavalry division and army artillery) was to connect this " prin- cipal attack" in Lorraine with the other "principal attack" mentioned below, first by holding the Cote de Meuse between Verdun and Toul, next by repelling sorties from Metz and blocking up the west front of that fortress, and lastly by giving support to the attacks of the neighbouring armies.
The V. Army (five corps, two reserve divisions, one cavalry division and army artillery) had to deal with two alternatives, those of violation or non-violation of Belgian territory. In the latter case, it was to drive eastward from its concentration area N. of Verdun and the Argonne across the Meuse, dropping in its progress a flank-guard to watch the Belgian frontier; its ob- jects were to defeat and drive northward all German forces en- countered, and to storm or invest, according to circumstances, the fortifications of Thionville (Diedenhofen), guarded and as- sisted on its right by the III. Army. In the first alternative, it was to be so disposed that it could both attack northeastward on Neufchateau and Florenville in the Ardennes, and guard its left rear with a special detachment.
The IV. Army (three corps, one cavalry division and army artillery), concentrated behind the III., was the general reserve. It was destined to be used either on the right -or on the left of the III. Army according to which of the two "principal" attacks Lorraine or Ardennes needed additional weight. If the offen- sive of the V. Army was directed upon Neufchateau and Floren- ville, the IV. Army was to come in between the V. and the III., and fight its way in the direction of Arlon. Behind the right were to be three reserve divisions, ready to follow up the VII. Corps and take over the guard of the Rhine as it advanced. Behind the left, but not definitely allocated to the V. Army, were to be three more reserve divisions about Vervins, with a somewhat indeter- minate mission. A corps of several cavalry divisions was to form about Mezieres in the first days of mobilization on the left of the protective system, and thereafter to operate eastward or northeastward into the Ardennes as required. Its supporting infantry was to occupy the bridges between Dinant and Namur if the Belgian Government did not do so.
This was the plan which was carried into effect when war came in August 1914. As early as Aug. 2, it was decided to act on the hypothesis of a German movement through the Belgian Ardennes, the seizure of Luxemburg by the German advanced- guards on that day being a sufficiently suspicious indication. But during the following days the French General Headquarters were confronted with a mass of definite and indefinite informa- tion which it was hard indeed to appraise; On the protective line, apart from two severe local fights, at Mangiennes in the Woevre and Lagarde in Lorraine the first a French, the second a German victory there were no events and no important indi- cations. To the N. of the left flank, want of liaison, and, it must be added, of mutual confidence, made it difficult for the French to gauge exactly what the Belgian army would do, and especially what was happening at Liege. That fortress was attacked on Aug. 5, and its capture (see LIEGE) was announced as a fait accompli on Aug. 7, yet for many days thereafter the gathering masses of the Germans between Aachen and the Ardennes seemed to make no move.
The British Expeditionary Force (four divisions and a cavalry division) was about to land in France, but it was not comprised in "Plan 17." A secret appendix to the plan, known to a few, provided for a hypothetical " Army W." landing from overseas and proceeding to the region of Valenciennes and Maubeuge, but the way in which this army (should it materialize) might best be employed could not be seen until the role of the French V. Army had become clearer. Meantime, it was to double the part of left echelon which was assigned to the French reserve formations about Vervins.
But meantime, the troop-trains were arriving in the concen- tration areas, and the broad " Plan 17 " had to be replaced by an-
