The Germans were the aggressors in World War One.
World War One began when Germany invaded Belgium and Austria-Hungary invaded Serbia.
Germany invaded Belgium - not only taking over a sovereign country (and committing vile atrocities against the populace) but also taking control of Antwerp and the Scheldt.
Britain guaranteed Belgian neutrality not only to curb Prussian and French territorial ambitions but to protect the Scheldt - a deep water port close to Britain that could be used to launch an invasion.
The German Confederation reneged on the Treaty of London when they invaded Belgium and brutalized its people. That vicious land-grab (along with the Austro-Hungarian attack on Serbia) was the real start of WW1.
Germany were just the first movers in a war that had all but started.
Russia was in E. Prussia within 2 weeks of Germany entering Belgium. A simple rain delay in the west would have made them the “agressors” if you think about it.
I personally see neither side as innocent. they all worked for war and postured to let the other guy take the fall so their flimsy aims didn’t become the reason it all went to heck.