Like many I was confused by the big balls of colour clinging resolutely to the backs of generals in the awesome Shogun 2. Soon the forum was covered in threads explaining their name and origin with a particular youtube video that discussed their use being heavily linked. It was a great video but there were a few misunderstandings that resulted from its tone and experiments.
People seem resolutely convinced that its name, derived from Japanese as "arrow catcher" meant it was clearly originally conceived as a peice of protective equipment to be used by important individuals "to protect them from arrows when retreating/routing". Now in all fairness this conclusion is nothing but logical. They are on the back, they entangle arrows so surely they were simply somewhat odd additions to Japanese defensive tailoring.
This is not the case. The Horo started its career as a pocket of silk that when attached to the back of a rider billowed prettily in the wind. Upon it was emblazoned the clan iconography and with the Japanese being unbelievably flamboyant in regards to their battlefield marketing it was soon widely adopted by ranking figures. Thus, it was in a short amount of time considered a great honour to wear but with most generals spending much of a battle stationary a somewhat caricature like evolution occurred. Bamboo was used as a frame to ensure it maintained its form while stationary and as time went on the size grew from a simple back hanging to a gargantuan form, often reaching several meters in diameter.
This popularity among the ranking was not because of its protection. If archers were a genuine concern for a Daiymo then he was probably close to loosing the battle anyway, indeed one is forced to ask if so little faith was put in his back plating to 'ensure his safety while fleeing' then why would his front armour be considered efficient. People in this forum seem to be under the assumption that it makes perfect sense for the paragons of Japanese manly virtues (namely nobles) who existed in an honour driven society to wear massive, obvious and clearly ungainly contraptions simply to assist in their odds of survival in case they need to leg it. No.
It was a ceremonial piece whose ability to entangle arrows was far from its original purpose. Indeed the name is considered by some (namely my professor... and me ) to have come from the days when messengers as well as generals would wear them meaning when they arrived to deliver reports the now deflated Horo would most likely be riddled with stray arrows that instead of simply bouncing of conventional lacquer had instead been 'caught'. It would only take one joke about the 'arrow catcher' for the name to stick and indeed slip into popular Japanese lexicon.
Again thanks to this youtube clip, people have gone on to say its clear second purpose was akin to that of a zebras stripes: disorientate the predator (archer). The presenter mentions in passing that he found aiming at the fluttering piece distracting. The cursory remarks of one historian are now TWC Horo gospel. This is clearly a pleasant side effect for messengers and runners, not one that was foremost in the mind of whatever Japanese retainer first sew it for his master.
Ultimately to pitch the Horo as a protective garment for fleeing nobility is like saying the banners every soldier wore above his head was a contraption that protected the wearer from weakened overhead strikes as it would soften the blow if a spear head was caught in the silk. Clearly, that's an accurate statement; the banner would make a crude head guard, but we obviously know it is used for identification and to convey pride in ones clan. The Horo is, although in our minds clearly weird, simply a ceremonial cloak with an entertaining name: NOT a piece of protection that prevents an honourable death on the battlefield for a routed general and instead lets them escape to safe place that allows him to commit Sepuku anyway...
Sorry for the rant, but thought some may appreciate a clarification. Watch that video by the way, its still interesting.
P.S The most iron hard counter to even the most dedicated "it was protection" evangelist is that the original fluttering Horo with naught but air maintaining its form worked as protection because the airtight silk allowed the entire cloak to act like an airbag in a crash when the arrow struck. The contained air would be released out the sides and this cushion of delicious newtonian physics would prevent full arrow penetration. By the time we reach Sengoku Japan the ceremonial Horo is all that remains and thanks to the wicker frame, would comprehensively fail to slow arrows to the same extent. The best example I can think of is get a friend to hold a piece of paper. If its held loosely with some give in the sheet, trying to stab though it with a pen will be hard. Much of the force will be dissipated by the give inherent in a relaxed sheet. If it was to be held taught though... he will have a biro stab wound Its the exact same principle. The original version was a ceremonial dress with a nice side effect. The one we see on our precious generals bodyguard is a ceremonial dress that thanks to the frame would just ensure all the blood from an arrow wound pools at the bottom of the silk instead of getting your horse and saddle damp No. Protection. At. All.