Owing to the difficulty of approaching the enemy trenches in the open, advances were made by pushing saps ahead, or by blowing them up with mines. On both sides incessant digging of galleries and mine-chambers went on underground, whence a race in speed and skill between the opposing sappers, for it was a case either of blowing up the enemy first, or being blown up by him. Over the mine-destroyed trenches, through the smoke and under the rain of earth and stones caused by the explosions, the soldiers dashed forward to occupy the new shell-crater, or to fight for it if the enemy had reached it first. Then would follow a bloody hand-to-hand struggle with grenades, knives, bayonets, daggers, axes, etc., resulting in the gain of a few yards of ground. From the end of 1914 to March 31, 1915, between Four-de-Paris and the Valley of the Aisne, the French sappers excavated over 3,000 yards of mine galleries, and fired fifty-two mine-chambers, using nearly 16,000 lbs. of explosives. The Stationary Warfare (_September, 1914, to September, 1918._) Activity on the Argonne front was greatest during the first year of the war. The German positions were held by part of the Army of the Crown Prince, whose technical adviser was the old Marshal von Haeseler. This army was composed mainly of first-class troops, including the XVIth (Metz) Corps, one of the best in Germany, and superior to the famous Prussian Guards. This Corps was commanded by General von Mudra, a sapper skilled in mine warfare, who had under his command numerous well-equipped pioneers. The French Divisions of the 5th and 2nd (Active) Corps, though inferior in equipment, outrivalled the enemy in courage and daring. They held the sector for many months, and their tenacity was more than a match for German technique. They quickly adapted themselves to the necessities of forest fighting, and from February, 1915, they were fully equal to the enemy in discipline and equipment. In October, 1914, the line, as a whole, crossed the entire width of the Argonne, from the north of Vienne-le-Château to the north of Neuvilly. As a matter of fact, there was no continuous line, the French troops holding only rudimentary trenches, as stationary warfare was still distasteful to them. They believed the pause to be but temporary, and that they would soon resume the advance. They constantly attacked the Germans, who, equally aggressive, endeavoured to gain ground, and to wear down the French resistance by attacks on trenches, and by ceaselessly-renewed local engagements.