‘a WW1 battle involving tanks (which I believe weren’t in existence then’
They were by the end of the war. The British Mk1 was the first tank to be mass produced and that came into service during WW1.
Tanks started showing up on the battlefield in 1916, and were active during the first world war
In the second world war there was a conflict between tanks and cavalry in Poland, and the cavalry bested the armored units, although only briefly:
The only major battle that took place between Japan and Germany was the siege of the German-controlled Chinese port of Tsingtao in Kiautschou Bay. The German forces held out from August until November 1914, under a total Japanese/British blockade, sustained artillery barrages and manpower odds of 6:1 – a fact that gave a morale boost during the siege as well as later in defeat.
After Japanese troops stormed the city, the German dead were buried at Tsingtao and the remaining troops were transported to Japan where they were treated with respect at places like the Bandō Prisoner of War camp.[23] In 1919, when Germany formally signed the Treaty of Versailles, all prisoners of war were set free and most returned to Europe.