Book Review: 98 Days - A Geographer's Review of the Vicksburg Campaign.

This is one of the most informative books I've read on the Vicksburg Campaign. While the prose is rather mediocre, Professor Grabau explains several things about the campaign that have always puzzled me. To whit:

•  1) Why was Vicksburg so important? Answer: Vicksburg and Port Hudson kept Union gunboats out of this 240 mile stretch of Mississippi, thereby allowing the Confederates to ship supplies down the Red River and across the Mississippi to the East. 
•  2) Why was the Black River considered a military obstacle despite its low water level in summer? Answer: The River has steep banks that retard movement by wagons or artillery no matter what the water level. Which is why fords and bridges were so important. Add that the uncleared banks were full of trees, brush, and fallen timber, and you can see why roads leading to fords and bridges were the only way over the river. 
•  3) Why were military operations in Mississippi difficult in mid to late Summer? Answer: Not only did most of the creeks and small lakes dry up, but the lack of well-water meant armies had to depend on farmers rainwater cisterns for water. And these cisterns weren't big enough to supply a large army with water. Both armies at Vicksburg had to transport water from the Mississippi or Yazoo to their troops. The Confederates by hand, the Union by water-wagon. 
•  4) Why were Civil war armies brought to a halt by rain? Roads contained neither gravel or rock, rain turned them to mud and the average Civil war wagon or Artillery piece had ground pressure PSI of 64. By comparison a Sherman Tank had a ground pressure PSI of 14. Result: the wagon or artillery soon sunk to its axles in mud.