Above: General U. S. Grant and staff, City Point, Va., summer of 1864. With the pressure of an election looming, in March of 1864, Lincoln appointed General Ulysses S. Grant to be commander of all the US armies. The war was far from decided and the fate of the Union was still uncertain. Source: Library of Congress, Public Domain. Click to enlarge.

After the Confederate defeat at Chattanooga, President Lincoln appointed General Ulysses S. Grant to the special regular army rank of General-in-chief (Lieutenant General) on March 2, 1864. Congress had previously authorized this rank only two other times, a full rank to George Washington and a Brevet rank to Winfield Scott. President Lincoln was reluctant to appoint Grant due to his possible ambition as a candidate in the upcoming Presidential Election of 1864, yet once made aware that Grant would not be eligible for candidacy he approved the promotion.

With his new rank, Grant moved his headquarters to the east and installed Maj. Gen. William Tecumseh Sherman as Commander of the Western Armies. Unbeknownst to the public at large, President Lincoln and General Grant held meetings in Washington D.C., formulating strategies for "total war" against the Confederacy, including targeted strikes on military, railroad and economic infrastructures.

Above: Lt. Gen. Ulysses S. Grant standing by a tree in front of a tent, Cold Harbor, Va. Mathew Brady Photographs of Civil War-Era Personalities and Scenes, between 1921–1940. This item documents the time period of ca. June 1864–ca. June 1864. Source: U.S. National Archives, Public Domain. Click to enlarge.

Grant also devised plans for coordinated campaigns between multiple armies operating simultaneously in separate theaters of operations such as Virginia and Georgia with objectives that focused on capturing strategic cities such as Atlanta and Petersburg while also applying pressure on more rural areas via raids by cavalry troops. This approach ultimately proved successful at destroying many of the Confederate resources necessary for them to continue their fight against Union forces throughout the conflict between North and South America during the Civil War period.

Further reading
In 2019, Liveright Publishing Corporation, a Division of W.W. Norton & Company published The Annotated Memoirs of Ulysses S. Grant, edited by Elizabeth D. Samet. Samet is a professor at West Point, the United States Military Academy. Her work received praise from scholars and historians from David W. Blight of Yale, and General David H. Petraeus among others. At 1,069 pages Samet's work makes a valuable addition to collections of Civil War buffs and readers alike. You can pick up the book here on Amazon. 

Prize-winning author Ron Chernow's Grant was published in 2017 by Penguin Press. Grant quickly became a #1 New Yorrk Times Bestseller, and Chernow has been called "... America's greatest biographer, bringing movingly to life one of our finest but most underappreciated presidents." Pick up Chernow's Grant here on Amazon.