Interesting that the default formation for modern infantry is the wedge, but for almost entirely different reasons.
Naw. Threads re-opened in GQ to add actual substance aren’t locked for zombification.
Medieval tactics have waited this long - they can survive being re-opened a few years later. 
If they were used, it would be because the defenders were in effect pinned in place after they established their shield-wall. It was very difficult to move the shield-wall to one side or the other - anything other than standing in place or moving forward would be difficult, requiring a level of training and generalship difficult to achieve in Medieval warfare.
The “wedge” really could be though of as - the very best man-killing warriors to the front, trailed closely by a (larger) column of the more ordinary, followed by the mass of the attacking shield-wall. I doubt it was a neatly pointed formation, for all the usual practical reasons - difficulty in arranging, difficulty in keeping co-ordinated on rough ground, etc.
It is sort of a riff on how ancient warriors (and those in less developed societies in our own time) fought - the “man killers” in front, each with a following of lesser warriors trailing them in support. The difference is that, rather than a bunch of individual duels, the “man killers” are all grouped together in one spot, part of an organized effort - aimed at breaking the line.
I admit it is something described in theory - I haven’t read of an actual battle in which these tactics were alleged to have been used. But then, you don’t often get a real tactical analysis of most ancient battles. The “Svinfylking” is certainly claimed to exist often enough. Tacitus claimed the Germans used a similar system against the Romans.
Why do you wedge modern infantry? To provide the most soldiers as possible with a clear field of fire?
Yeah, overlapping fields of fire over 250 or so degrees + covering the flanks while on the move + increased visibility all around + each soldier depending on their position in the wedge can be assigned and drilled into watching a specific sector at all times so they don’t get caught unaware or distracted.
Whereas a straight line would mean only two guys able to imperfectly watch the sides while a straight column would mean much less frontal firepower and an overly grumpy [del]sniper bait[/del] point man :).
BTW these general principles also apply to tank, HMMWV or even plane formations. Wedges and Finger Fours see a lot of use.
I haven’t been to the SDMB in a long time and came back on a lark. I cannot believe how much I have forgotten in 12 years. I could not have this discussion today.
This is one of my favorite threads.
I was going back and reading some materials by medieval historians and came to the conclusion that… we have no idea. We know next to nothing about how those soldiers actually fought. And most of what we do know about earlier soldiers is even thinner, even when we don’t realize it. (For example, we often rely heavily on the works of a couple Roman authors for descriptions of their military, but both have issues.)
The Franks didn’t leave a whole lot of written materials about their actual fighting. They clearly did think about it and passed around military treatises, but it was pretty evident that their commanders learned by experience and didn’t necessarily write their tactical or strategic choices down. They also seem to have been surprisingly flexible in battle, since what we do know suggests they were constantly trying different dispositions.