other words, Luxemburg might have been used as the infallible means of
dragging us into every and any war which might arise between Germany and
France. From that danger we were protected by Lord Stanley's objection;
as the case stands the treaty gives us, in his own words, 'a right to
make war, but would not necessarily impose the obligation,' should
Luxemburg be attacked. To this doctrine a reference will be found in the
British White Paper (No. 148), where Sir Edward Grey informs M. Cambon
of 'the doctrine' concerning Luxemburg, 'laid down by Lord Derby and
Lord Clarendon in 1867'. It may also be observed that two of the
co-guarantors of the Treaty of 1867, namely Italy and Holland, have also
not thought it necessary to make the violation of Luxemburg a _casus
belli_.


III

It is evident to all who study closely the map of France that her
eastern frontier falls into two sharply contrasted divisions, the
north-eastern which reaches from the sea to the valley of the Sambre,
and the south-eastern which extends from that river to, and along the
Swiss boundary. The former is flat country, easy for military
operations; the latter is mountainous, intersected with many deep
valleys. After the loss of Alsace-Lorraine, the French set to work to
rectify artificially the strategical weakness of their frontier; and in
a chain of fortresses behind the Vosges Mountains they erected a rampart
which has the reputation of being impregnable. This is the line Belfort,
Épinal, Toul, Verdun. A German attack launched upon this line without
violating neutral territory would have to be frontal, for on the north
the line is covered by the neutral states of Belgium and Luxemburg,
while on the south, although the gap between the Vosges and the Swiss