Vicksburg was nicknamed "The Gibraltar of the Confederacy." No large Union boats could sail the Mississippi past it without drawing cannon fire and likely being sunk -- the Union had dug a canal to avoid Vicksburg but it was too shallow for big boats. Union forces under General Grant, whose star had been steadily riding since the fall of Fort Donelson had been trying for a long time to get at Vicksburg -- there had been seven failures trying to get Union forces to where they could assault Vicksburg, and all the Union did was create a growing casualty list, and public opinion that General Grant was a fool, a drunkard, or worse.
"All Grant's schemes have failed," observed Elihu Washburn, long Grant's congressional benefactor who elevated the West Pointer to brigadier general early in the war. One newspaper editor colorfully put it (quoted in Shelby Foote, Fredericksburg to Meridian pg. 217), "Well, now, for God's sake say that Genl Grant, entrusted with our greatest army, is a jackass in the original package. He is a poor drunken imbecile. He is a poor stick sober, and he is most of the time more than half drunk, and much of the time idiotically drunk."
In answer to his critics, in his memoirs Personal Memoirs of U.S. Grant, Grant had to say (ch. 32),
- I took no steps to answer these complaints, but continued to do my duty, as I understand it, to the best of my ability.
- For two months Grant's army had been floundering in the mud. Many of them rested permanently below the mud, victims of pneumonia or dysentery or any of a dozen other maladies. Vicksburg stood as defiant as ever.
- ... General Johnston suspected that the Federals in the Mississippi Valley held a winning hand if they played it right.
- A direct attack from the Mississippi,
- Pull back on Memphis, going overland, or
- March the army down the west side of the Mississippi, cross the river south of Vicksburg, and attack from the south and the east.
The Louisiana shore west of Vicksburg was not much more forgiving, riven with streams and poor country roads, and on the wrong side of the river. Retreating to Memphis, Tennessee and taking the railroad down, east of the primeval Yazoo Delta made sense, but that would be an admission of defeat, and Northern public opinion would condemn the already-shaky Grant. He chose the third plan.
Grant had political considerations with which to deal as well. Henry Halleck ("Old Brains," above him in Washington) was of a cautious bent, and Grant knew he might oppose the dangerous naval expedition. The Union fleet could be lost or crippled; Grant was to place his troops where a Confederate force of unknown size might destroy them; and the Union supply line down the Mississippi was in grave danger of being snapped, leaving an entire Union army cut off.
Some on Grant's staff and other Union generals such as Sherman and General James B. McPherson opposed the dangerous plan. Sherman recommended falling back to Memphis and going down from there.
Grant's plan was thus far more dangerous than one gets from one-paragraph summaries in American history texts.