The machine gun was one of the many weapons used during war. The main purpose of this gun was to kill people faster, which it accomplished. Instead of using a rifle, which fired one bullet at a time, the machine gun could fire 400-600 small calibre rounds per minute. This gun was most effective while fighting in the trenches. Before the machine gun, men had to fire and aim at one person, but when using the machine gun you were able to spray people down, not having to take careful aim.
Tanks were motorized armored vehicles used as assault weapons. The tank rolled on caterpillar tracks which allowed mobility throughout thick mud. Although the tank moved at four miles per hour, it was still a huge use in warfare along with trench warfare. Troops could rise out of their trenches and follow behind the tanks that would lead the way through enemy barbed wire and shield the infantry from withering machine gun fire.
Submarines or "U-Boats" were new technology introduced during WWI that could get close to enemy ships and sink them without being seen. With this great stealth, they were used to attack the ships and other military targets of the enemy. Attacking these ships resulted in naval blockades and restrictions on movement of supplies over the ocean.
Poison gas, which was of course a gas or vapor was used widely throughout war to kill or disable enemies. The gas was most effective in trench wars. Although only 4% of overall soldiers died from poison gas, it was still feared. The gas was able to draw soldiers out of trenches leaving them wide in the open, and if soldiers didn't quickly put their masks on they were in great danger.
Sources: "Tanks and World War One". HistoryLearningSite.co.uk. 2014. Web.
"Germans Introduce Poison Gas." History.com. A&E Television Networks, n.d. Web. 11 Jan. 2015.