Your basic longsword is about 4 feet long and about 3 lbs in weight. Longswords are built either for unarmoured or armoured combat, or built to make a compromise between the two.
Longswords built for armoured combat have a stiff blade, aggressively pointed. This is to facilitate the powerful thrusts required to defeat armour. The last few inches will be very sharp. Designs differ, but there will often be some provision for grasping the blade with your off-hand (this is known as "half-swording") - either the whole blade will be sharp save for a hand-sized portion in the middle of the last third, or only the tip will be sharp. Some longswords designed for armoured combat will have the quillons sharpened to points, to allow devastating quillon punches and mortschlags (more on that later).
|An armoured man holding his sword in "half-sword".|
Longswords built for unarmoured combat will have a more flexible blade, sharp all the way down. It may not be quite as aggressively pointed.
I'd like to clarify that the "unsharpened" portions are not totally dull, they're just not nearly as sharp as the rest of the sword.
The longsword, despite being a weapon of status, was not typically the primary battlefield weapon of armoured men, who typically preferred spears or poleaxes. The longsword was primarily a sidearm or a self-defence weapon.
Much like the arming sword, the cuts are delivered by pushing the balance point forward not with big swinging arm movements - . The big difference with a two-handed sword is that you do a "lever" action with your two hands, moving your right hand forward and your left hand back to snap the tip forward faster and more powerfully.
While half-swording (illustrated above) is possible with an arming sword, the extra 8" of blade (the other 4" of increased length over an arming sword is in the handle) really does make half-swording a longsword more viable.
Half-swording basically turns your sword into a small spear, and many of the spear plays are possible with the half-sword. It provides a powerful defence that can easily transition into a powerful thrust, and because it gets you in close, it puts you in a great position to enter and get into grappling.
Both Fiore and Vadi say, "the sword is an axe". While this statement is rather cryptic alone, by looking to the German tradition, we see a technique called the "mortschlag", or "murder-blow".
|From historicalfencing.com - a mortschlag delivered to the vulnerable back of the shoulder.|
The mortschlag involves grasping the blade with both hands, and swinging the sword exactly like an axe or mace. Ringeck advises that mortschlags be delivered to the foot, the hand or arm, or to the back of the hip or shoulder. Tallhoffer (I think - I know some of my readers are better versed in the German tradition than I am, and will surely correct me) describes used the crossguard to hook and disarm from mortschlag.
The other side of the comment "the sword is an axe" is, in my opinion, that the sword and the axe share, amongst the knightly weapons, that is equally capable of thrusts and blows.
The other thing worth mentioning is that the sword can be used as an extra lever in holds, locks, or disarms. The point of the half-sword can be slipped between the arm and the sword and twisted for a disarm. If you can get behind your opponent, the sword can be held against their throat with a hand on the blade and one on the handle for a choke-out, severe neck wound, or a throw. When applying certain keys, the sword can be used to help lock up the arm and provide additional leverage for a break or throw.
In defence the longsword is used much like arming sword except at the half-sword, so that's what I'll discuss here.
Much like the spear, the half-sword can be used to knock a blow or thrust aside and immediately counter with a thrust of your own, or blow right through into a pommel/quillon strike.
|From this block, you can turn your sword to the right, simultaneously displacing your opponents sword and directing your point at his face or neck, or come to a grapple as we see below.|
Once you've blocked or parried at the half-sword, you're going to be very close to your opponent, and many defences in armour revolve around grappling. A man in armour is extremely well-protected, and throwing him to the ground is a great way to neutralize that advantage. Working at the half-sword facilitates this.
|Coming to an arm lock - the opponent can be forced to the ground from here. If they strongly resist the throw, their arm will break.|
|From here, you can throw your opponent to the ground by pushing back on his head with the tip of your sword. Obviously, if he doesn't have good neck protection, he'll be severely injured even before he hits the ground.|
|A possible follow-on from the first half-sword defense I showed - push forward and slip the sword behind the neck, then use that powerful grip to hurl the opponent face-first into the ground.|