aug 18, 1892 - Franco-Russian Alliance
Description:
The Franco-Russian Military Convention was signed two years after the German-Russian Reinsurance Treaty had been allowed by Russia to lapse. France and Russia, fearing attack by central powers, came together.
In short, should France or Russia be attacked by one of the Triple Alliance signatories - or even should a Triple Alliance power mobilize against either, the other power would provide military assistance.
https://www.firstworldwar.com/source/francorussianmilitaryconvention.htm
Added to timeline:
Date: