In Abraham Lincoln's first days as president of the U.S.A. he settled on a strategy--Oh, strategy would be giving it too much forethought--he developed a bent of mind that was to become a strategy: everything that could be done (sometimes extra-legally and unconstitutionally) would be done to suppress the rebellion and restore the Union.  His first request of Congress was for $4,000,000 and 400,000 men, goodly amounts in 1861. Every power that the federal government possessed (and some it didn't) was put in service of the war.

But civil war was a new thing to Americans that did not come with how-to manuals. Soldiers and officers on both sides had, in some cases, served together under the stars and stripes in the Mexican War (Scott and Lee for instance). Both spoke the same language. Both had until very recently been part of a larger whole.  So in the early days of the actual fighting it was not entirely uncommon for a soldier, or even a civilian, to make complaint to the commanding officer of the opposing forces for relief from the actions of the men under his command. 

At first Lincoln issued a dictum that civilians and their property were to be spared collateral damage of war. The earliest real battles were fought in Virginia, in the Shenandoah Valley, so rich a food source that it could have fed the armies of both sides even when at full strength. Cue Louis CK if God came back. "Why are you eating hardtack? Just eat the shit I put on the floor!" Nah, ah, ah said Father Abraham. For the most part the Yankees obeyed and ate hardtack.

A Virginia officer went to Butler and asked for the return of run-away slaves who U.S. soldiers had taken in. "Undah the Constitution, suh, they ah the propahtee of their ownahs." "Virginia claims to be an independent nation," Butler replied. "The Constitution of the United States does not apply to foreign nations." Butler had created a new word for the slaves, "contrabands", and they were manumitted. The War Department ratified his seat-of-the-pants legal dialectic. This did this small practical necessity become mother to the invention of emancipation as a principal aim of U.S. policy.

Sometimes an officer on one side would go to his counter and ask a hypothetical, "What would you do if we did---?". It was all very irregular. In one of these instances the U.S. officer responded, "Bomb". Cannonade you back into the Union, kill every last one of you, was the longer, unstated, implied, astonishing answer. Cue Pink Panther.

"Beum?"
"What?"
"You said 'beum.'
"Yes, I know that, we will bombard you and shoot you and make you howl."

And they did. 

Lincoln's bent of mind greatly simplified his task. He had distilled the U.S. war aim and its methods down to its salty, residual essence and it became by degrees strategy for the remainder of the war. U.S. soldiers gave no quarter. Confederate civilians and their property, real or chattel, became co-belligerents with their government's troops. William Tecumseh Sherman also gave the language of war a new term, "scorched earth." In his March to the Sea Sherman burned everything in his path that he and his soldiers could not use. It was "total war," a corollary military term. The Confederate states and their people were to be destroyed. And they were.