When I wrote on the evolution of the Japanese sword I described the transition between tachi and katana but one thing I didnt mention was a little grey area between 1469 and 1532 when a particular type of sword that was just slightly smaller than its predecessors, made its first appearance. This sword is described as 'Kata-te-Uchi' and that translates roughly to 'straight hand draw'.
An example of a Kata-te-Uchi, the single handed sword style derived from the two handed uchigatana, popular during the Sengoku period.
The period of time that this sword came to exist in was turbulent, the sengoku period (also called the 'warring nations period') being a time of war, with the daimyo asserting more control over their localities, often fighting with each other bitterly over land and political power. It was because of this that many katana in this style were produced, often of greatly varying quality. This isn't to say that all swords during this period were like this of course, but it was a bit hit and miss. These less beautiful pieces are easily recognised by collectors and are not well favoured. I mean we know what happens when a forge mass produces swords, the number goes way up and quality control plummets. You can imagine how in a time of war, this quality control was probably the last thing on the minds of the smiths. For this reason, a lot of these swords were sold in bulk amounts both inside and outside Japan. It says something when swords like this are sold in bundles.
But regardless of construction quality, functionally the kata-te-uchi style was exceptionally good for one thing, to allow the swordsman to more easily manipulate the sword with just one hand. A longer tsuka is fantastic for two handed styles because it gives you the room to properly place both hands and that affords more control and power in each cut. For single handed use however, it falters and the reason for this is because the tsuka can actually get in the way when it's not being controlled by your 'off' hand. There are in fact styles or methods that expressly tackle the difficulties of one handed sword use.
Another kata-te-uchi example, this time in tensho style koshirae.
With kata-te-uchi, the tsuka was shortened considerably in order to ensure it didnt get in the way. The swords actual cutting edge however, was shorter than the tachi, roughly the length of normal katana, but the nakago or tang was significantly so. The reduction in overall length made the sword more easily manipulable with just one hand although the weight of the actual blade remained approximately the same. This and the fact that in many examples, there was no appreciable difference in the width of the blade from the monouchi to the base near the habaki meant that the kata-te-uchi style led to a stouter but more top heavy sword in some cases.
Kata-te-uchi because of it's advantages at the time, stuck around for a number of years but eventually it of course evolved again under new demands and the overall length increased and the original tsuka returned to facilitate two handed use. It's important to know however that this style never replaced the tachi or indeed get in the way of the concurrent evolution of the uchigatana, but it is interesting to see a relatively sudden and obvious sideline on the japanese swords evolutionary path caused by another instance of conflict and unrest. Every little aspect of the history of these swords contributes to the katana as we know it today and to not pay attention would be silly.