Shoup himself, postwar, said he was in the council of war with Johnston and his corps commanders, and that he promoted leaving a small force to defend the Shoupade line, which Sherman would have had to besiege to reduce, while the balance army crossed the rvier and maneuvered to block Sherman's crossings... But this was declined.
Description based on: v. 2, no. 1 (Jan. 1894); title from cover
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In his post war narrative, General Johnston simply notes of the Shoupade line on the Chattahoochee:
General Johnston does not appear to have been inclined to have left any part of his army in the Shoupade line while General Sherman's forces were outflanking it and crossing the river upriver from it.
In his memoir, Vol. 2, General Sherman explains that while the Shoupade line was incredibly strong, it was limited in extent... and he quickly moved to outflank it, and cross the river beyond it... and then, had Johnston left any troops there, to have cut them off.
So Sherman Thought Johnston had left a corps to hold the Shoupade line and fell back across the river... and made his subsequent moves upon that idea (which at the time was incorrect).
Shermans' troops affected a crossing of the Chattahoochee on the 9th of July, and that night General Johnston evacuated his army across the river, abandoning the Shoupade line. Sherman in his memoirs, by which time he was aware that Johnston's army had actually not yet crossed the river, thought Johnston's only lost opportunity here was in not striking out from the Shoupade line upon his flanking columns moving to cross upriver: in other words, if anything, that Johnston remained in the cover of the Shoupades too long, rather than too briefly.