刚去查了一下靠谱文献，是30英里X70英里，但不是你说的四光。对寡孤老人，单身妇女和孤儿的房产领地不许动（见下）：

https://www.nps.gov/articles/000/the-burning-shenandoah-valley-in-flames.htm

Thirteen Days of Destruction

Sheridan commenced a dramatic war on the countryside on September 26,1864 that would last for thirteen days. The destruction would begin in Staunton and head down the Valley, northward to Strasburg, covering a length of 70 miles and a width of 30 miles. This destruction infamously became known for generations simply as "The Burning." Sheridan ordered his men to move fast, destroy everything that could be useful to the enemy, then move on quickly to new targets. He also instructed them to spare houses, empty barns, property of widows, single women, orphans and to refrain from looting. Col. James H. Kidd of Custer's brigade described the scenes as they set fire to a mill in Port Republic:

"What I saw there is burned into my memory. The anguish pictured in their faces would have melted any heart not seared by the horrors and 'necessities' of war. It was too much for me and at the first moment that duty would permit I hurried from the scene."