A few points:
Firstly, grabbing a spear requires that the grabber has a free hand - and if you are in a shield-wall, you don't really want to let go of your shield or your weapon if you can help it (even if you have a sword knot or similar strap connecting your wrist, it will take you time to recover it). Also, any attack will create openings which your opponents can exploit - grabbing with your hand is likely to put it in harm's way beyond the protection of your shield. By the way: the reason why chess pawns capture diagonally is apparently because the people on either side of your direct opponent in the shield wall are best placed to take advantage of openings in your defence - if you have a long enough weapon (like a spear). This was evidently as true in India a few thousand years ago (when chess was invented) as it was in the 1700s when english soldiers were supposedly taught to do this with bayonets fixed on muskets, against sword-and-shield armed highlanders in the jacobite rebellion.
Regarding the "rugby scrum with swords and shields", although I think this might be true of pre-Alexander ancient greek phalanx tactics, my understanding is that from roman times onward, soldiers usually fought in a slightly more open formation, with enough space to wield their weapons. Vegetius certainly thought they should:
Quote: |
No part of drill is more essential in action than for soldiers to keep their ranks with the greatest exactness, without opening or closing too much. Troops too much crowded can never fight as they ought, and only embarrass one another. If their order is too open and loose, they give the enemy an opportunity of penetrating. Whenever this happens and they are attacked in the rear, universal disorder and confusion are inevitable. Recruits should therefore be constantly in the field, drawn up by the roll and formed at first into a single rank. They should learn to dress in a straight line and to keep an equal and just distance between man and man.. |
As unreliable as it admittedly is, Migration-era and early medieval art suggests that this practise continued after the fall of the Roman empire - there are usually at least some gaps between soldiers in the line, even in the Bayeux tapestry I think. There are obviously tactical reasons for sometimes bunching up and overlapping shields (probably when facing a heavy missile barrage), but it isn't a forgone conclusion that they'll adopt it.
Also, by not locking shields and scrumming up, you get to use the shields dynamically, for instance deflecting attacks and hooking other shields and weapons rather than just as a static barrier. Using a shield this way is apparently much more effective, and is recommended in most of the later fencing manuals which cover any sort of shield, as well as those people attempting to understand viking-era shield usage based on the sagas and experimentation. In fact, the only time that I can think of offhand where shields were definitely used statically on foot were the big pavises used to defend crossbowmen. And it is not just the people of early renaissance Europe who used shields in this way. Less than two hundred years ago, the Zulu people of my country were using large, oval center-gripped shields (about as wide and much higher than migration-era roundshields) with short stabbing spears, clubs and axes to carve out an empire for themselves against other peoples who are supposed to have predominately used thrown spears, perhaps with long clubs (knobkirries) as a sidarm. They fought in a formation which could be compared with a shield wall (although with encircling arms on the flanks) but they did not lock shields, and they used their shields dynamically in the method described above. They also didn't wear a scrap of body armour, not even a helmet, so armour is at least not necessary for successful shock-troops (and successful they were, as any survivors of the british army they defeated Isandlwana would attest). While it is obviously not reasonable to say that the Zulu armies are directly comparable to those of migration-era Europe, it is at least interesting to look at them as a more recent and verifiable example of how large shields may be used on a pre-gunpowder battlefield.
Finally, have a look at this picture (again, from the renaissance, but bear with me)
http://wiktenauer.com/wiki/Paulus_Hector_Mair...ail_01.jpg
It is from a fencing manual depicting techniques for fencing with the big, heavy flails that peasants used to thresh wheat with.
If people fighting with those things can benefit from using proper techniques, a smaller, lighter migration-era sword certainly would.