Correction.
It
is a swordsman's weapon, translated as "Long Saber". That is basically what it is. It dates to the Ming Dynasty, and was designed by Qi Jiguang for use on the Northern Border. it is based on the Japanese Nodachi that Qi Jiguang had seen the Wokou use, and had an anti-cavalry function.
From Thomas Chen's site:QUOTE
These large 2-handed sabers were first used by the Northern Border Troops under the command of Ming General Qi Jiguang in the late 1560s-70s to deal with Mongol cavalry, and remained in use right up to the late Ming (1620s-1644). At that time, these sabers had an overall specified length of 1.95 meters. General Qi, who lived from 1528-1587, had written the influential training manual "Lian Bing Shi Ji" while he was the commanding and training officer for several northern units bordering Mongolia. Commanding about 100,000 men, some of the best troops of the Ming empire, he had successfully deterred Mongol aggression at the border for over 10 years.
QUOTE
One simple and specific training technique for General Qi's soldiers wielding the Miao Dao is to setup two thick wooden poles, one short and one long, spaced 2 feet apart.
The soldier will then use the Chang Dao like a zhanmadao, bending low while advancing and striking first at the bottom part of the shorter pole to simulate cutting through the horse's legs, afterwhich he will raise and turn slightly to strike the upper part of the longer pole, simulating the strike on the horse's head -- A practical scenario for when the horse dies, the enemy soldier/rider loses his mobility and becomes meat on the platter for the Chinese soldiers.
General Qi had also stipulated compulsory 2-person combat drills using wooden sticks for mock practice, for use in his army.
The Changdao was issued to musketeers and a good deal of the non-artillery troops under Qi Jiguang.
I believe Fireball's perception of the Chang Dao is of the long handled glaives sometimes used by cavalry (a la the Yin Yue Dao/Guan Dao), and her idea of a "Sword" is that of a Jian (which would have been fairly out of place by the Ming Dynasty as a sword for infantry swordsmen, who would have used Dao).
Also, in my opinion, Dao is best translated as "Saber", as "Knife" would imply a small, short bladed tool (though I suppose the translation is better than "broadsword"). A saber though carries the connotation of a sword-length usually military weapon with a single edge (and usually a curve), though I prefer to apply the term to Zhi Bei Dao (straight backed Dao) as well.