Upper Oka Principalities

'Upper Principalities') traditionally applies to about a dozen tiny and ephemeral polities situated along the upper course of the Oka River at the turn of the 14th and 15th centuries.

[citation needed] Following the Mongol invasion of Kievan Rus' of 1223–1240, the formerly prominent Olgovichi clan of the Principality of Chernigov gradually declined to a point where the descendants of Mikhail of Chernigov (died 1246) ruled dozens of quasi-sovereign entities.

[citation needed] The strengthening alliance of Lithuanian rulers with Roman Catholic Poland caused shifts in the balance of power in the region.

Most Orthodox rulers of the Upper Oka Principalities, therefore, started to look to Moscow for protection against Lithuanian expansionism.

[citation needed] Others sought Lithuanian protection against Muscovite aggression, such as Prince Ivan of Mozhaysk who in 1454 fled to Lithuania to escape from Vasily II of Moscow.