world war 1

Main article: Western Front (World War I)
Military tactics before World War I had failed to keep pace with advances in technology. It demanded the building of impressive defence systems, which out-of-date tactics could not break through for most of the war. Barbed wire was a significant hindrance to massed infantry advances. Artillery, vastly more lethal than in the 1870s, coupled with machine guns, made crossing open ground very difficult. The Germans introduced poison gas; it soon became used by both sides, though it never proved decisive in winning a battle. Its effects were brutal, however, causing slow and painful death, and poison gas became one of the most-feared and best-remembered horrors of the war. Commanders on both sides failed to develop tactics for breaking through entrenched positions without heavy casualties.[citation needed] In time, however, technology began also to yield new offensive weapons, such as the tank. Britain and France were its primary users; the Germans employed captured Allied tanks and small numbers of their own design.