It is debatable whether there was actually a complete breakthrough and whether the stalemate was ever fully broken. The Germans were never forced back to fight on home soil or ever completely conquered. However, it was the Germans

The Blockading Of German Ports

• After the battle of Jutland the British navy focused on stopping ships getting to German ports. This was not very successful initially but it started to affect the Germans in the 4th year.
• They did this for several reasons; firstly if cargo ships could not reach Germany then Germany’s supply of valuable resources such as food, fuel and weapons would dry up. Also if the ports were blockaded enemy battleships and destroyers could not attack British and French ships or coastal towns. This meant that there could be no naval invasion of Britain.
• The British achieved the blockade by laying mines across the entrance to the Baltic Sea (Sweden to Holland) and across the top of the North Sea (Scotland to Norway). Therefore if German ships made it past the Baltic minefield they could either risk the North Sea one or go down through the channel where they would be bombarded by the British and French. These mines prevented almost all German ships, with the exception of U-boats from leaving port.
• The effect of this tactic was that Germany slowly began to run out of resources without the supplies coming in from overseas.
• The Germans could either surrender instead of running out of supplies, or go for one final offensive. Either way, the stalemate would be broken. The chose to go for one final offensive.
• The Germans also rebelled against the blockade by creating a big U-boat force to act as a counter blockade. This was very successful and it was calculated that Britain was down to its last five weeks of food when Lloyd George invested in anti submarine devices and this situation was turned around.

The German Offensive (Spring 1918)

• This was the Germans final attempt to break the deadlock, also known as the Ludendorf Offensive. The German army has been bolstered by moving troops over to the Western Front from the East.
• The Germans broke through the ranks of the British and tried to get as far as they could. This was a massive attack and it made a big bulge in The Allies line, with some of Germany’s elite (The Storm troopers) advancing as much as 50 metres in the line.
• This was said to be a tactical move since the French aimed to draw the Germans in, then encircle them and attack them. This counter attack was in fact successful and pushed the Germans back more than what they had advanced. This attack was made more successful by America pushing troops in and reinforcing the line.
• Since the Germans put everything into this attack, they were unable to sustain this war. This was a rare battle of mobility and this meant the breaking of the stalemate, which eventually led to the Germans agreeing to a cease fire and seeking an armistice with the Allies.

New Technology/Weapons

• The tank was so successful because it countered the three inventions which had caused the deadlock; trenches, barbed wire and machine guns. The tank could easily drive over barbed wire and trenches because of its caterpillar tracks and length respectively and machine gun bullets simply bounced off it. This meant that a tank could easily cross no mans land and destroy an enemy’s defences breaking the deadlock on a certain part of the front.
• However, they were generally mechanically unreliable and unsound, with commanders unsure of how to use them effectively, technically or strategically. The infantry also could not keep up with them and they were used in isolation, with a chunk of them breaking down before even reaching the enemy lines. Also, they relied on support from behind, to refill with petrol. By the end of the war, they were being used far more effectively, in formation. They were used to great effect at Amiens in 1918.
• In this war, airpower was mainly used for observation and spying, as they had a very limited flying range, were not strategic and had a lack of space. In the early stages, there were many casualties from poor landings and simply falling from the sky.  They were also very inaccurate, and did very little damage to enemy trenches or supply lines.

• Gases like chlorine were also used as a weapon. They were put into the air to damage oncoming enemy troops and to restrict their breathing. This was unreliable as if the wind changed direction, it could back fire killing your own troops.