Originally posted by: BeauJangles
Originally posted by: Arkaign
Originally posted by: SphinxnihpS
Everything used in the war was developed prior to the war.
For the most part this is true. There were a number of things used for the first time in a major conflict though.
I'd have to go with Uboats. Yes, submarines existed prior to WWI, and IIRC one was even used briefly in the US civil war. But there had never been a full naval effort at subs as a legitimate branch of a naval force. Subs have played a massive global role ever since.
The same arguments could be used for airplanes, but airplanes weren't packing much of a punch in those days. Mostly valuable for recon.
Machine guns and artillery had already been used in other conflicts, and although they were certainly the dominant means of killing the enemy and holding the lines for each side, I can't really single them out. It's pretty typical for a major conflict to see the use of newer/better guns/arty.
Right, gatling guns had been used by colonial empires against indigenous people and they'd be used sparing in actual wars. To dismiss the World War I machine gun is pretty silly, considering the beast that took the battlefield in WW1 was entirely like any other machine gun that had been fielded previously. In fact, the Maxim gun offered something that had never been seen on a European battlefield -- self-powered rapid-fire guns. These weapons didn't just "hold the line" or any other such nonsense, they dramatically changed the way the war had to be fought. Grand strategy had to be change due to this weapon and its new-found power.
The submarine also made a big splash in combat during World War I and, while the Germans had some success, the submarine ultimately failed to break the naval blockade that plagued Germany or to do crippling or long-term damage to the Royal Navy. Yes, they sank a lot of ships. At their peak, they were sinking ~2 ships per day. They ranged across the globe and triggered the First Battle of the Atlantic, but they ultimately lost that battle. Submarines might be one of the more interesting weapons deployed in WW1, but they are far from the most important. The original question wasn't about most important, but I feel that the conversation has definitely drifted that way.