Tactical.

But Jackson, an artillery officer who understood the tactical implications of his position, was pushing ahead on his own. He wrote Lee on May 7 that he had finished reconnoitering Maryland Heights and had “determined to fortify them at once, and hold them, as well as the Virginia Heights and the town, be the cost what it may.” Be the cost what it may. In case he had not made himself perfectly clear, later in the same letter he stated, “I am of the opinion that this place should be defended with the spirit which actuated the defenders of Thermopylae.”  His reference was to the 480 BC battle in which 7,000 Greeks held off 100,000 or more invading Persians for seven days before succumbing. Jackson’s carefully chosen image is strikingly bloody, epic, and absolute in a war that had seen very little bloodshed. On May 9 Jackson wrote Lee again to report that he had placed five hundred troops on Maryland Heights, prompting this scolding retort from Lee: “I fear you have been premature,” he told Jackson. “The true policy is to act on the defensive and not invite attack. If not too late you might withdraw until the proper time.” Lee also pointed out the political repercussions of Jackson’s rash moves: “Your intention to fortify the heights of Maryland may interrupt our friendly arrangements with that state, and we have no right to intrude on her soul unless under pressing necessity for defense.”

In any case, it was too late.  The troops would stay. But Jackson, after proving his mettle as an administrator, had now begun to build a reputation as something less desirable—an officer who was overeager and required close watching by a superior officer, and who, above all, needed to be reined in. In his movement into Maryland he was completely at odds with the political climate in Richmond and with individual politicians such as Jefferson Davis, who were deeply suspicious of him.

This was in part Jackson’s own fault. He was motivated by the belief that, for the South to win against obvious industrial and numerical odds, it would have to win quickly. That meant hitting the enemy’s green troops hard and soon, and not paying attention to such political niceties as state boundaries.  That meant burning Baltimore and Philadelphia and making Northerners understand on a visceral level what this war was going to cost them. As early as the week after secession, Jackson had proposed to Virginia governor John Letcher the idea he had mentioned in the letter to his nephew in January: a war of invasion in which the South would fly the “black flag”—meaning that all Union prisoners would be summarily executed. He even proposed to set the example himself.

Though his plan sounded bloody, brutal, and un-Christian, as Jackson saw it there was clear and practical logic behind it. “He affirmed that this would in the end be the truest humanity,” wrote Robert Dabney, “because it would shorten the contest, and prove economical of the blood of both parties ...  This startling opinion he calmly sustained in conversation, many months after, [saying that since] the Confederate Authorities had seen fit to pursue the other policy, he had cheerfully acquiesced.”  But he still believed it. As for his then-radical idea for a war of invasion, he was simply ahead of his time. By the second year of the war, Robert E. Lee would come to the same conclusion. He would eventually invade the North twice. Jackson’s notion of total war, meanwhile, would soon define the entire conflict on both sides. The final campaigns of Union generals Grant, Sherman, and Sheridan in 1864 and 1865 were the fulfillment of Jackson’s ideas.  For now, however, they were seen as wildly aggressive, if not outright crazy.

S.C. Gwynne, from Rebel Yell: The Violence, Passion, and Redemption of Stonewall Jackson