There were several new inventions used in World War I. Both the Allies and the Central Powers had new weapons to use.
In 1914, the Germans used the Zeppelin airship that could be used for dropping bombs. The Germans also developed a gun that could fire a huge shell over a long distance. In 1915, the Germans began to use chlorine gas. Chlorine gas can be deadly if inhaled. They also used the flamethrower. The flamethrower was a weapon the allowed a burning liquid to be directed in a stream at the enemy. Germany also began to use gas shells in 1916. Finally, Germany developed the submarine and used it to do sneak attacks on Allied ships as the ships were crossing the Atlantic Ocean.
The Allies had some inventions of their own. The British were the first to use tracer ammunition. This allowed a pilot to see where he was firing. The Allies began to use gas masks to counter the German use of chemical warfare. The British developed and used the tank in World War I. The United States also uses the Browning machine gun in 1917.
Both sides used airplanes in World War I. However, airplanes would be much more of a factor in World War II. New inventions helped both sides fight in World War I.