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 (shm[)a]n d[=a] dahm); while the Canadians secured Passchendaele (pahss-ken-d[)e]l’[=a]) 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-br[)e]’; 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-m[)e]r’), 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 army in a single bombing expedition.

THE RUSSIAN REVOLUTION.—­In 1917 the Allied cause received a heavy blow through the collapse of the Russian government.  Long before the war there had been parties in Russia which desired to do away with the autocratic government of the Czar and substitute some sort of representative system which would give to the people a voice in the management of their affairs.  These reforming parties did not agree among themselves as to the kind of government they wished to set up; their ideas extended from limited monarchy of the English type, all the way to anarchy, which means no government at all.  In 1905 the Czar met the wishes of the reformers to the extent of establishing the Duma, a sort of representative assembly or parliament, which should help in making the laws.  The Duma, however, was never given any real authority, and as time passed those who believed in Russian democracy became more and more dissatisfied.