Sickles move forward against orders before the onset of day 2 at Gettysburg:
Was anything really lost (or gained) by him moving forward ahead of the Federal line? Leaving the line and creating a gap in it isn't the brightest but when all was said and done, did his follie really do any damage? I'm not sticking up for the crazy nut, I'm just curious from a tactical side of it.
In my opinion, he created a glass jaw for Longstreet to hit. There were several weaknesses to Sickles deployment forward:
1) It created three open flanks for the Confederates to hit. (both of his and Hancock's left were exposed)
2) It created a salient in the lines.
3) It disrupted Meade's defensive scheme, forced the use of troops otherwise intended as a reserve and forced Meade to weaken his line elsewhere.
4) The line he adopted had some 400 yd gaps between Ward and DeTrobriand and a gap between DeTrobriand and Graham (These had to be plugged by artillery, some of Burling's men and reinforcements from Caldwell and Barnes.)
5) It was too long a line for a corps of a shade less than 10,000 men.
6) Third Corps was organizationally ill-suited to adopt the extended position. (It was a two division corps, which meant that only Burling's men were in reserve, instead of the standard two divisions forward, one in reserve alignment). Burling became a supernumerary and his brigade was parceled out a regiment at a time to cover weaknesses in the line.
7) Instead of being anchored on LRT, his left hung in the wind.
8) Instead of being connected to Hancock, his right was hanging.
9) He moved farther away from rear and flank support (Had he stayed put, Fifth Corps was 15 minutes away, after the move, they were 45 minutes away.)
10) He disobeyed orders.
11) Given Longstreet's orders, and his unwillingness to veer from them because of Lee's rigidness that morning (which was fed by Johnston's failed recon mission), he would have presented his right flank to Sickles if he deployed as ordered.
12) Reinforcements from Second and Fifth Corps had to come in piecemeal because of the lay of the land.
13) The AotP suffered more than 2,000 more casualties than Longstreet trying to defend and cover the retreat of Sickles' Corps.
Those are pretty compelling reasons revealing the larger ramifications of Sickles' mistake.