The French development of La Guerre Miasmatique has had a major impact on warfare on Earth and the other colonised planets. Batteries firing chemical and bacteriological agents across the battlefield cause thousands of casualties whilst typhoid snipers target individual soldiers for disease and death.
Whilst despised by many, if not for the French introduction of this new and virulent form of warfare it may have been that Earth would have fallen to the Martian invader in 1901. It was the French Empire's Corps Medical Offensif and the diseases they fired at the tripod encased invaders which caused the Martians destruction.
All major powers now have developed their own units of chemical warfare troops, but the French still lead the way in their development and use.