The Four Most Stupid Battles

The Battle of the Somme
The Battle of the Somme deserves a mention in this list, not because the tactical value was amiss, but rather because of the immense stupidity of the commanding officers such as General Douglas Haig.
The tactics, if indeed they can be called that revolved around a series of relatively small and inaccurate artillery strikes, many of which would not have been able to breach the German bunkers. To aid the artillery strikes several large mines were detonated ten minutes before the infantry moved to take the objectives. 

The detonation of these mines early could be called the most stupid action if only it wasn’t for the decision that ‘the infantry would only have to walk over to take possession’. The Germans had taken cover in their bunkers to avoid the shelling, knowing that advancing infantry would be able to reach the fortifications before they would be able to set up their heavy machine guns. By detonating the mines ten minutes early the Germans had more than enough time to set up their heavy weapons, and then it was a simple matter of blasting away at the British who were casually walking over no-man’s land. All in all around 60,000 people died during the course of this battle, for only a small gain in territory.

Charge of the Light Brigade
The Charge of the Light Brigade gets an honourable mention here due to it not actually being the tactics that lead to such horrendous losses, but rather it was because of a simple miscommunication.
Rather than harry a retreating Russian artillery battery the British light cavalry were ordered to charge against a different artillery battery, one that was set up with excellent fields of fire, and had supporting defensive fire.
This charge was an abject failure, as although the Light Brigade actually managed to reach the artillery battery, they were so badly mauled that they had to retreat immediately, having gained no land, having failed in their mis-communicated objective and having suffered huge losses.

Battle of the Hornburg
The Battle of the Hornburg is different from the others listed here for the obvious reason that it didn’t actually happen. However so stupid are the tactics used in this battle that I felt it required a mention.
Wikipedia suggests that there were at least five Uruk-hai to each Rohirrim, plus of course the men of Dunland, creating a massively mismatched battle.
I am focusing primarily upon the adapted film version where the elves come to aid the Rohirrim for it is the elves, with Aragorn ‘leading’ them who commit the most foolish actions. When the wall is breached by Saruman’s bombs the elves fire one arrow each into the narrow gap in the walls killing literally every Uruk-hai who had breached them for no elvish losses. Had they remained and continued shooting arrows then the deeping wall would likely not have fallen or, at the very least, would have held longer. Now you might be thinking that the elves had run out of arrows before they charged, yet you can clearly see quivers almost full in some cases on the backs of the elves. Thus they decided that, although they were expert shots, they were more willing to meet an enemy in close combat, an enemy that in every way exceeded them, in numbers, in strength and ferocity.

The Vietnam War
The Vietnam War is also somewhat different from anything else in this in the fact that it is a war, however it seems apt to include it since in every way this was a blunder.
I’ll keep this entry short as I don’t have a huge knowledge of the Vietnam War, besides that it was one where all the wealth and technology of America couldn’t beat some villagers poorly armed and equipped by the Chinese.
In order to gain some form of advantage the American military committed crimes against humanity that still have effects today, dumping napalm, agent orange and a series of other weapons all of which are now outlawed, all of which cannot be used in war.
Despite this they were utterly unable to defeat the Vietnamese and after riots in America and thousands of deaths the Americans pulled out and the communists took over South Vietnam shortly after. In total 58,220 American soldiers died, along with 2-300,000 Cambodians, 20,000-200,000 Laotians and anywhere between less than one million to more than three million Vietnamese.