During the American Civil War, controlling the Mississippi River was an important part of the overall Union strategy for two reasons. It would, first of all, cut the South in two and thereby weaken it militarily and otherwise. Second, it would open up the Deep South to invasion by Union land forces.
To have control of the boats and trade.
Siezing control of the Mississippi River was an important goal of the Union Navy because it was the major means of transportation and logistical communications in the U.S. interior.
The Northern generals, particularly General Ulysses S. Grant, aimed to control the Mississippi River as part of their Anaconda Plan. By seizing key points along the river, they intended to divide the Confederacy, cutting off supplies and reinforcements between the eastern and western states. This strategy would cripple the South's logistical capabilities and weaken their ability to wage war. Ultimately, control of the river would also allow Union forces to move troops and resources more freely throughout the region.
The word that means to catch or take by force is "capture." It implies seizing control or possession of something or someone, often through strength or strategy. In various contexts, it can refer to apprehending a person, taking control of territory, or securing an object.
Coup d'état
After seizing control of the Assembly, the radicals wrote a new declaration of rights and constitution modeled after the USA.
John Brown
Seizing
The Union Strategy was known as the Anaconda Plan. Scott's plan involved blockading southern ports and seizing control of the Mississippi River Valley, depriving the South of supplies or the ability to easily transport troops and supplies, squeezing the life out of the Confederacy. Later commanders elaborated on the plan by adding control of the Cumberland and Tennessee Rivers and, later still, adding Total War to completely destroy the South's infrastructure, causing the complete collapse of the economy and preventing supplies from getting to the soldiers in the field, and destroying enemy military and civilian morale.
Seizing, you spelt it correctly.
opportunity seizing
Because the French felt that they should punish them.