The two strategies used by the Union during the Civil War were:
- Naval blockade - The Union implemented a naval blockade of Southern ports to cut off supplies and trade.
- Seizing control of the Mississippi River - The Union aimed to gain control of the Mississippi River to divide the Confederacy and facilitate transportation and supply movement.
The other two responses, "defensive war" and "relying on European countries for supplies," were not strategies primarily associated with the Union during the Civil War.