<P> However, the British commander in Upper Canada received news of the American declaration of war much faster . In response to the U.S. declaration of war, Isaac Brock issued a proclamation alerting the citizenry in Upper Canada of the state of war and urging all military personnel "to be vigilant in the discharge of their duty" to prevent communication with the enemy and to arrest anyone suspected of helping the Americans . He also issued orders to the commander of the British post at Fort St. Joseph to initiate offensive operations against U.S. forces in northern Michigan, who it turned out, were not yet aware of their own government's declaration of war . The resulting Siege of Fort Mackinac on July 17 was the first major land engagement of the war, and ended in an easy British victory . </P> <P> The war was conducted in three theatres: </P> <Ol> <Li> The Great Lakes and the Canadian frontier </Li> <Li> At sea, principally the Atlantic Ocean and the east coast of North America </Li> <Li> The Southern states and southwestern territories </Li> </Ol> <Li> The Great Lakes and the Canadian frontier </Li>

Where did the war take place in 1812
find me the text answering this question