How would the Union winning the war give "a new birth of freedom" to the
United States?

The Union winning the war give a new birth of freedom to everyone.

Explanation:

The winning of the war by the Union led to the beginning of a new beginning for the nation. It was the nation's efforts to come to terms with the destruction of slavery and freedom for all. For American President Abraham Lincoln, its meaning focused on an idea explained clearly in the Declaration of Independence, that all men are created equal. In other words, it gave African American freedom to vote, to own property, and become part of American citizenship.

b or c ( this is because my answer is short so just ignore it)

c. troops marched forward in close formation against newer, more accurate weapons