There also were attempts by the Union's ironclad fleet to run the gauntlet of the guns.
An indication of how central those efforts to take the city were to the Union campaign, it is not until about two-thirds through Groom's narrative that Grant gets his army across the river some 24 miles south of the city in an amphibious operation that stands with Washington's crossing of the Delaware.
Groom calls the eighth attempt, a 200-mile loop through the rivers and bayous north of the city, as "one of the strangest wartime expeditions in naval history." Because of flooding, the ironclads that led the armada were often steaming higher than the drowned houses and forests on the riverbanks.
"Not only that," Groom writes, "but the trees and branches were inhabited by all species of swamp creatures that had sought refuge from the flood." Whenever a ship bumped into one of these trees, "its decks were immediately inundated with . . . live zoological specimens: 'coons, possums, snakes of all descriptions and temperaments." Sailors tried to sweep them overboard, but some resisted which, Groom comments, "made life aboard ship more interesting."
When Grant's troops were finally across the Mississippi and advancing on Vicksburg from the east, they encountered, Groom writes, "[a] puzzling, tortuous terrain . . . [of] hills, valleys, folds, dead-end gulches."
Up to this point in his account, Groom has focused on the strategies and tactics devised by Union and Confederate commanders. There is little from common soldiers, and only one civilian voice. But that, of Kate Stone, a young woman living on a plantation across the river from Vicksburg, is a revealing one, describing such domestic matters of a family in a war zone as the conclusion that coffee made from okra seed was a better substitute than that made from "parched potatoes, parched pindars, burned meal, roasted acorns."
But once Grant has invested Vicksburg, civilian voices assume greater importance in Groom's narrative.
Readers of a certain age may be reminded of World War II air-raid shelters by descriptions of the caves dug into the bluffs on which Vicksburg sat.
