By early 1915, no side was able to decisively push the other across the Seine and France's east-central highlands. The Siege of Paris is the most notable battle of this period, claiming the lives of over two million Entente and German soldiers. Practically every building in the city was quickly reduced to rubble by artillery fire. During both 1915 and 1916, the Germans enjoyed unparalleled air superiority in what was later known as the Fokker Scourge; German Fokker fighter and bomber planes were vastly superior to Entente ones, while the German pilot program had seen far more pre-war preparation and wartime funding. Entente reconnaissance planes could not direct artillery fire nor observe enemy positions, while German ones could almost unopposed. As a side note, German trenchworks were usually better built and maintained. While the stalemate developed, Entente forces unsuccessfully tried to relieve Paris through offensive operations in the Battle of Rouen and the Battle of Troyes, employing their industrial and manpower superiority. The British, especially, made ample use of Indian forces in unsupported human wave attacks, almost always disastrously. In Rouen, over a million Indian soldiers perished, disappointing the Indian public and fanning the flames of a future revolution.
To solve these issues, the Germans began to plan for a three-pronged strategy known as Unternehmen Zeidrack (Operation Trident).
- The Kaiserliche Marine would play with the Royal Navy; they would ensnare small flotillas against the former's High Seas Fleet. If the latter's Grand Fleet showed up in force, Germany's technologically and numerically superior torpedo destroyers and submarines would engage them in a series of skirmishes, attempting to divide them once more. This plan was favoured over the long-term and far less decisive convoy raiding strategy that some KM admirals proposed. Furthermore, German naval aviation would develop, train and organise torpedo bomber squadrons to act as a force multiplier over the seas, employing them aggressively against capital ships.
- The Deutsches Heer would prepare novel armaments and tactics, unleashing them at a decisive moment to break the Entente lines.
- First, Austro-Hungarian engineer Gunther Burstyn's proposal for the Motorgeschütz, a cross-country motor vehicle armed with an artillery cannon and/or machineguns, developed parallel to British efforts to bring about the first tank. These were envisioned to break through enemy lines, through mud and trenches, in combined-arms armoured spearheads.
- Second, legendary colonial fighter General Paul von Lettow-Vorbeck, who was stranded on leave in Germany and could not travel to command his troops in Africa, proposed the formation of infantry troops trained in infiltration, stealth and close quarters combat using pistols, grenades and carbines; the Sturmtruppen (or Stormtroopers). Russia's Brusilov Offensive in mid-1916, in which infiltration tactics were used for the first time, proved this approach as feasible.
- Third, IG Farben and other German chemical industry companies would produce as much chlorine and phosgene as possible, while the Deutsches Heer would prepare methods for disseminating this new deadly gas, mainly through artillery.
- Fourth, the armaments industry would prepare a number of firearms more suited for close-range warfare, most notably automatic C96 pistols and shortened bolt-action rifles.
- Fifth, a large number of new Flammenwerfer (or flamethrower) units would be produced and attached to large infantry units, making trench, bunker and tunnel defence harder.
- Finally, the novel, well-trained and expansive Deutsche Luftstreitkräfte (German Air Force) would mass their aircraft and develop a series of tactics mostly aimed at harassing and destroying the enemy's rear, or the first interdiction tactics.
- Surplus fighter aircraft, which were not needed for contesting the air against Entente interceptors, would have their pilots trained on directly engaging enemy air defence using their machineguns in the first suppression of enemy air defences (SEAD) operations. They would also carry small bombs and be instructed to attack enemy trucks, artillery batteries, storage depots, trains, field hospital, command posts, etc.
- Bombers would be mainly employed against the same targets as the former fighter-bombers, but with greater payloads.
- Heavy bombers would mainly be used to disrupt France's industrial centres and ports, preventing them from using British and American supplies to reinforce.
With almost two years to prepare, Unternehmen Zeidrack was finally put into action on the 26th of October, 1916, in what became the Battle of Dijon. It was this success which would lead to German victory in World War I.