Did Vikings (or any nation in the Early Middle Ages) use longswords? Some say that two-handed swords appeared in the XIV-XV centuries because of the development of plate armor, but I know that longswords were used by Scottish mountain men and Irish gallogases who didn't wear plate armor so armor is not a key for longsword use. That's why I wonder if it was used earlier, and if not - why?
Did Vikings use longswords?
The short answer: No.
There is one sword that you might see pictures of if you search for "Viking longsword":
but, as I discussed there, the grip is would have been about 11.5-12cm, which is common enough for Baltic long-gripped (but still one-handed) Viking swords, which usually have grips of about 10-12cm. Note that most of the pommel is missing (only the pommel cap remains); this estimate assumes that the main part of the pommel (the "upper guard") was the same thickness as the guard (the "lower guard"). The blade of this sword is narrow for a Viking sword, only about 4cm wide, which makes the grip appear longer in photos.
There were Viking-era swords in Northern Europe with long grips allowing two-handed use. A famous example is the "seax of Beagnoth":
The tang is 17cm long, and if it was a typical seax hilt with a burned-in stick tang, the hilt would have been longer than that. However, with a not-huge 55cm of blade, and a total weight (when intact) of little more than 1kg, it's far from a longsword. It would not have required two hands to use. This shorter seax:
has a 14cm tang, and again could easily have had a grip usable in two hands, but with only 32cm blade, it's even less of a longsword. Another example:
shows that these long-hilted seaxes were not so rare.
Did Vikings (or any nation in the Early Middle Ages) use longswords?
Two-handed swords (of the type called "great sword", "great sword of war", or "sword of war" at the time) appear in the mid-12th century (or at least, that's when the oldest ones found probably date to). There are examples and discussion of these in Ewart Oakeshott's Records of the Medieval Sword (and these are also discussed in his other books, e.g., in The Sword in the Age of Chivalry). For some photos of such early two-handers, see http://myarmoury.com/talk/viewtopic.8309.html
Thus, we don't know of any early Medieval European "longswords". Swords with one-handed grips were at least occasionally used two-handed in the Early Middle Ages, judging by art and literary sources. For some examples of such art, see
Why might there have been no long swords with two-handed grips at this time in Europe? First, note that long hilts aren't free. They make the sword less convenient to wear (which matters with a weapon that one wears everywhere, every day). Early Viking swords appear to often have had scabbard slides as their suspension mechanism. We don't know for certain how such swords were worn, but a good reconstruction is passing a baldric through the scabbard slide, with the sword between baldric and body. The sword can be held more stably by wearing a waist belt around the sword, holding it against the body. This is a convenient way to wear a sword, since it keeps the blade clear of the legs, and the sword is easily drawn. However, the hilt is fairly high up on the left side of the body, and a two-handed hilt could easily be awkward. For a photo of a sword worn like this (and note where the hilt is), see about 2/3 or 3/4 of the way down this page:
Also, a sword with a long grip is harder to use with a shield even when used one-handed (the hilt can catch on the shield).
Noting that two-handed spears, large two-handed axes, and some unidentified-but-described-as-effective polearms (e.g., the aetgeir) were used, there were weapons that would play a similar role in battle, but better. What need then for a two-handed sword?
Elsewhere, two-handed swords were used in the Early Middle Ages, or even in Antiquity. For example, this Indian cave art shows a two-handed sword:
which is possibly of Sassanid origin (in the hands of a Sassanid ambassador?). Two-handed swords were used in China from the Han Dynasty onwards, and some of them qualify as "longswords". Some Tang examples are shown on
We know very little about the details of the use of these early Asian two-handed swords - literary sources are lacking. At least some of them were balanced very similarly to late Medieval European cut-thrust longswords (i.e., with the pivot point very close to the tip, which is also common on many cut-thrust one-handed swords (e.g., Ming/Qing jian, European smallswords) because it gives very good point control), so it's possible that many of the techniques were similar (OTOH, there aren't that many different ways to hold, parry with, cut with, and thrust with a two-handed sword, so even without such apparently similar handling, many of the techniques would be similar).
