Answer: The union invasion was to capture the Confederate cities of Vicksburg and Port Hudson in other to have absolute control over Mississippi River.
Explanation: In the year 1863, Union army invaded port Hudson to win the control of the Confederate cities of Vicksburg and Port Hudson,The invasion was to have absolute control over the Mississippi River. After Port Hudson and the confederate soldiers surrendered, the Union Army then had absolute power over the River of Mississippi which is their primary objectives.