At the beginning of World War I in 1914, the German army started the Western Front by invading Luxembourg and Belgium. They gained military control of many important industrial regions in France. Their quick advance was stopped by the Battle of the Marne. Both sides then dug defensive trenches. The trenches eventually reached from the North Sea to the Swiss border with France. During the years between 1915 and 1917, many offensives were started from these trenches. Both sides used large numbers of artillery and thousands of infantry in these offensives. However, a combination of entrenchments, machine gun nests, barbed wire, and artillery stopped these advances. No major breakthroughs happened. New military technology, like poison gas, aircraft, and tanks were developed to try and get through these lines of trenches.