Well Struck!
For one of my projects on linen armour, I had to quickly check a reference to the memoirs of Usāmah Ibn-Munqidh, a garrulous old pirate with lots of tall tales about fighting and hunting and the barbarous customs of the Franks. As I was flipping through it, I discovered another story which I want to share.
The Ismāˁīlites … attacked the Castle of Shayzar (in 1109 or 1114 CE) … On that day I had an encounter with an Ismāˁīlite, who had a dagger in his hand, while I had my sword. He rushed on me with a dagger, and I hit him in the middle of his forearm as he was grasping the handle of the dagger in his hand and holding the blade close to his forearm. My blow cut off about four inches of the blade and cut his forearm in two in the middle. The mark of the edge of the dagger was left on the edge of my sword. An artisan in our town, seeing it, said, “I can remove this dent from it.” But I said, “Leave it as it is. This is the best thing in my sword.” The trace is there to the present day. Whenever one sees it he knows it is the trace of a knife.
– Philip K. Hitti, An Arab-Syrian Gentleman and Warrior in the Period of the Crusades: Memoirs of Usāmah Ibn-Munqidh (Columbia University Press: New York, 1929) pp. 146, 147 https://archive.org/details/AnArab-SyrianGentlemanAndWarriorInThePeriodOfTheCrusadesMemoirsOfUsamaIbn-Munqidh-PhilipK.Hitti/page/n155/
Foreigners who are not up on the details of Islamic theology call the Ismāˁīlites the Assassins after the hashish which they were said to consume. Shaizar is at a ford of the Orontes River in Syria.
Fiore teaches this way of parrying a sword with a dagger, but he recommends doing it with a sweeping motion and offline footwork not simply putting your arm between your body and the sword. One reason why its not really possible or useful to measure the penetrating power of muscle-powered weapons is that just things like whether the target is moving forward or backwards (or whether one party is one horseback) can make a significant difference in energy and momentum.
Usāmah gives us an important detail in explaining that he struck in the middle of the forearm and broke off 4″ of the blade. A heavy fighting knife can easily be a quarter-inch / 6 mm thick at the guard, but he struck near the tip where the blade was probably more like an eighth of an inch / 2-3 mm thick.
Its also plausible there was a flaw in the dagger, either a fracture in the blade which had already weakened it, or a piece of stony material in the iron, or a bad weld between layers of steel and iron. Some people today pay great sums to have smiths carefully imitate ways of using bad iron or steel with beautiful homogeneous materials, thinking that these old techniques are ‘better’ in all circumstances instead of a way of working around the limits of bloomery iron.
Usāmah was clearly impressed by his sword, since he left the mark on the blade and showed it to anyone who was interested.
But regardless, that was well struck!
This site is not going to throw itself onto a sword any time soon! But if you want to support it, and just sharing it with friends is not enough, I accept donations through Patreon or paypal.me or even liberapay
Edit 2020-12-13: Paul Wagner found a number of English and Scottish writers of the 18th and 19th century who recommend this kind of parry with a dirk or a naval pistol (Lt. William Pringle Green’s manuscript on training sailors to repel boarders and William Gordon Alexander, Recollections of a Highland Subaltern, During the campaigns of the 93rd Highlanders under Colin Campbell (1898) pp. 248-249 https://archive.org/details/recollectionsah00alexgoog/page/n294/mode/2up
Edit 2022-07-19: fixed formatting broken when WordPress introduced the block editor
If I am understanding it correctly, it is a ~9″ to 10″ blade. Hitting it hard would drive it against the forearm, allowing a solid full energy transfer to the narrow dagger blade as the forearm holds in place. Good chance the arm is broken even if the blade wasn’t snapped/cleaved in two. It is obvious why the advice is to use the dagger to deflect rather than a straight up block.
Of course it is possible the Assassin tried that, and either misjudged or Usāmah was just too fast.
It has been too long since I practiced the technique, and I was never good enough to do it at full speed and power, but the play of the wrist can steal some energy from the cut and then the flat of the dagger spreads the impact over the arm. OTOH, if your arm is beaten inwards, then the cut might still connect with your head. But its interesting to see this kind of sword versus knife match outside the salle, and to see an equipment failure deciding the encounter.