The Federalists were opposed to the War of 1812 because it would interfere with British trade relations. The Federalists considered England to be a great commercial ally, and since the Federalists were quite in favor of staying wealthy, they didn't want to risk ruining their connections.
For the following reasons the Federalists opposed the war of 1812:
1. They saw it as a war of the party designed to promote the concerns of Republicans and to quell the opposition.
2. They also apprehended that the war would drive the country into the arms of Napoleon.
3. Federalists recapitulated to defend the war since they recognised it an "offensive" war beamed at Canada. Although ready to sustain a war to defend American business or to protect the nation's boundaries, they declined to allow the subjugation of Canada.