What happened in the final phase of the civil war?

Answer 1

Two main campaigns that brought the war to an end.

In Virginia, Grant conducted a relentless campaign of attrition against Lee's Army of Northern Virginia, knowing that the Confederates could not replace their battle-losses. (Grant had ended the system of prisoner exchange.)

In Georgia, Sherman devised an entirely new strategy of attacking the infrastructure that supported the Confederate armies in the fields - wrecking farms and railroads, leaving the enemy troops barefoot and starving by the time of the surrender.