why does it matter if it was designed to fight people in a war or designed to fight people in an alley way. To be effective at one it must be equal effective at the other
Well, no, that's not so at all.
The environment "on the battlefield" tends to be dramatically different from that of most places in civilian life, including an alley. Particularly when we are talking about historic, pre-gunpowder/pre-modern martial applications, a ton of things which dramatically impact strategy, tactics, technique, and equipment are, frankly, different.
Let's look at a few.
Armor is a big one. All the way up to modern warfare, personal armor on the battlefield is the norm. From the Hoplite breastplate, to the Roman lorica, from the medieval chain hauberk, to the modern PASGT vests, personal armor is the norm when "in combat." However, their extra bulk, discomfort, and expense makes them fairly uncommon for Joe Sixpack citizen's daily use. This difference alone immediately necessitates changes in technique, targeting, and weaponry. These changes are very clearly expressed in the martial art.
Next is the weapons. Frankly the weapons most frequently used on "the battlefield" are optimized for group combat. Historically speaking, these tend to be pole-weapons and distance weapons such as long spears, long axes, javelins, bows, slings, etc. While a 12 foot spear makes a whole lot of sense for a warrior in formation it is pretty cumbersome for the civilian. Even in the cases where swords are used, it turns out that the swords used on "the battlefield" are frequently not the same as what works best in civilian self defense. The Odachi and Nodachi are certainly different from a Katana, and there are parallels in every culture. The Smallsword, which was primarily a civilian sword sure looks (and is used) different from a Longsword or basket-hilted broadsword. In a Chinese context does anyone expect a fairly light Jian to be the most efficient design for group combat? It's called the "scholar's sword" for a reason, right?
I mentioned "group combat" and "formations" a couple of times so let's talk about friends. In a "battlefield" fight, formations are life and death. If the formation breaks or the line collapses into general scrimmage, the army dies. For millennia military texts have been written on what formations to use, how to ensure their integrity, and how to break them. In a civilian self defense context, seeing an opponent as part of a highly organized and disciplined formation is pretty rare.
Lighting is another element which tends to be different. While not as hard and fast a rule as armor, most battles tend to be fought in the daylight. Generals and armies like to be able to see the fight. Conversely, civilian attackers like to use the dark of night to pick out unsuspecting and unprepared victims.
That is another difference; opponent as opposed to victim. The mind set of people on either side of a conflict is different between a military engagement and a civilian self defense encounter.
That said, I think we do agree on one part of what I believe you are trying to say. Humans are still humans. They only break in so many ways. A dislocated shoulder is effective whether "on the battlefield" or "in a dark alley." But there are, indeed, a lot of differences as well.
Peace favor your sword,
Kirk
