Subsequent to the battle that began at Gettysburg ended on July 4, 1863 (at the same time as the fall of Vicksburg) with a decisive but costly Confederate victory, General Robert E. Lee and his troops march on Washington, D.C. They launch an assault, hoping that if they can take the capital, they can win the war.
Meanwhile, President Abraham Lincoln has appointed Major General Ulysses S. Grant, the victor of Vicksburg, as commander of all Union forces and ordered him to attack Lee. Grant masses his forces (the newly minted Army of the Susquehanna) at Harrisburg, Pennsylvania, while Maj. Gen. Daniel E. Sickles gains control (through his violent pacification of the New York Draft Riots) of the Army of the Potomac.
Sickles has his eye on the White House, but he needs to defeat Lee in order to win the Civil War for the War Democrats. Violating orders from Grant, Sickles mobilizes his troops to meet Lee's army alone. A sidebar shows Napoleon III planning to have France invade the United States through its client state, the Second Mexican Empire.
Repulsed at Fort Stevens outside Washington (where the black troops of the 54th Massachusetts Infantry regiment played a decisive role), Lee turns on Baltimore. Abandoned by the Union, Baltimore descends into chaos; Lee, sickened by the violence, orders the provost guard in force to end it. Using Baltimore to threaten Washington, D.C., Lee turns his entire army upon the advancing Sickles, facing off at the former site of Joppa along the Gunpowder River northeast of Baltimore.
Lee destroys the Army of the Potomac in a rout, with Sickles losing a leg in the process (as he did historically in the Battle of Gettysburg). The battle pens Lee up in Maryland, however. Generals Grant and William T. Sherman converge on Virginia via Pennsylvania and Georgia. Lee scrambles to meet Grant's threat.
