Gaining control of the missisipi river during the civil war would allow the north to

It'd allow the North to control goods going down the river to the South. Doing this, the North could cut off food or weapon supply to "starve out" the other side. The North could also use the Mississippi for transporting their own troops into battle.

Chemical weapons became deadly, as did other aspects of warfare.

Explanation:

The knowledge about the affects and impact of chemical weapons was always known to people for a long time. However, it gained more concern only during the early 1900s after the Germans used first large-scale use of chemical at Ypres, Belgium in 1915.

The world has seen its damage and affects for the first time in real warfare and it truly gave a thrilling experience to the people around the world. People started to believe that modern weaponary and chemical weapons could have devastating affects and consequences. Thus, the trend 'Chemical weapons became deadly, as did other aspects of warfare' emerged concerning chemical weapons during the early 1900s.