Two very important ridges, from which artillery could reach German
positions, were taken during the heavy fighting in November. The French
forced a retreat of the Germans over a thirteen-mile front and occupied
the ridge known as Chemin des Dames (shmăn dā dahm); while the Canadians
secured Passchendaele (pahss-ken-dĕl´ā) Ridge.

Late in the year the British introduced a new method of warfare. Instead
of beginning their attack with a great bombardment lasting many hours
and thus indicating to the enemy the approximate time and place of
attack, they sent over the front a large number of "tanks" which broke
through the barbed wire entanglements and opened the way for the
infantry. By this means the British successfully surprised the enemy in
the battle of Cambrai (cahn-brĕ´; November 20 to December 13).
Unfortunately they could not hold most of the land occupied,--which was
lost later in the battle,--but they did show the possibility of breaking
the old deadlock of trench righting. The new method was to be used by
both sides during the campaigns of the following year.

THE WAR IN THE AIR.--During this year warfare in the air continued to
advance. Guynemer (geen-mĕr´), the great French ace, who was lost on
September 11, had to his credit the destruction of fifty-four enemy
machines. The increase in the number of airplanes led to the grouping of
large numbers into regular formations (escadrilles), sometimes composed
of over a hundred planes. Each year showed a steady increase in the
effectiveness of this kind of warfare. In 1916 a total of 611 enemy
machines had been destroyed or damaged by the Allied forces. In 1917 the
French destroyed forty-three in twenty-four hours; and the British
brought down thirty-one enemy planes in one combat. In a single week in
1918 the Allies destroyed 339 German planes. On one day, October 9,
1918, three hundred and fifty airplanes were sent forth by the American