How did peter the great expand russia’s borders? a. he gained control of a warm-water port along the black sea and defeated the vast ottoman empire, taking over their lands. b. he gained control of poland and took over parts of austria in a petition signed by peter, frederick the great, and emperor joseph ii. c. he defeated the swedes to gain control of the land along the baltic sea, and he signed a treaty with china to gain rights to lands north of manchuria. d. he successfully built the strongest army in europe and blockaded each border of russia to prevent mass migration to russian lands.