Worst military mistakes.

[Fiddler]

Somebody beat me to the punch! I was thinking that little mistake had to be mentioned.

And it is a terrible and kind of stupid tactical decision, because its essentially a massed long-range infantry charge unsupported by artillery against a heavily-entrenched artillery-supported enemy position which, by the way, also enjoys the benefit of greater manpower. All in all it's a no-no situation for any commander. Surprising why Lee, who had until then proved to be very capable and skilled, would commit such an ultimately crippling blunder.

Actually, Lee concentrated over 170 guns to soften up the enemy line, drive away the artillery and secure the advance of the infantry. The officer in charge, porter alexander, even assembled a dozen or so short ranged howitzers to accompany the infantry and support them in the charge, only to have them reassigned by Pendleton, Lee's Chief of artillery (IMO completely underqualified for this position). In addition, Lee envisioned attacks on the flank in support of the main thrust, but bad battlefield communication meant that Ewell attacked and was beaten back before Longstreet gave the signal to attack.
I love to quote Picket, who, after the war, replied to the question why the attack had failed "why, I always thougth the Yankees had something to do with it".