Day of Victory of Prince Alexander Nevsky's Warriors Over the Teutonic Knights on Lake Chud in 1242
Do not confuse Lake Chud with Lake C.H.U.D. On the other hand, go ahead and confuse them. I like to picture the C.H.U.D.s cheering on Nevsky's warriors and licking their chops at the upcoming meal of Teutonic Tartar.
It is traditional to feast on Teutonic Tartar on this occasion. Tartar sauce is optional, but being mayonnaise-based it is a nearly obligatory option.