Canada's Hundred Days. Aka the last 100 days of WW1.
Functionally, Canada won WW1 for the allies.
Being under 10% of the WW1 force, in that period they tackled defences everyone else thought impregnable and shattered them, like the Hindenburg Line, and in the process paved the way for the allied advance. They also took out a quarter of the German forces in that time.
While they did arguably use proto-blitzkrieg tactics of using lots of machine guns, and then also using vehicles to move troops even quicker while using said machine guns, one of the biggest factors was a prodigious use of chemical weapons.
To the point that in the interwar period, Canada had the largest capacity and stores of chemical weapons. During WW2, said stockpile is one of the reasons Hitler refused to use chemical weapons on the allies.
Edit: And a lot of the rules on fair treatment of POWs and rules on capturing surrendered soldiers also stems of Canadian soldiers behaviours during WW1.