How Effective were Spears Against Cavalry?

[Domen]

a good example of trained horses not shy of getting into a melee

Indeed, it should also be mentioned that horses fight in melee between themselves.

For example during breeding seasons, stallions fight in a very aggresive way.

I think the greatest advantage spears have on cavalry is their reach.

Exactly.

But this is why a cavalry lance was developed - and why it was later becoming longer and longer.

Probably longest lances in history were used by Polish-Lithuanian Hussars, to counter enemy pikes.

As Macedon already wrote - this issue was discussed in many threads before (Polish Hussars as well).

===========================================

Let's quote everything from that Chinese text which I quoted in the thread about chariots:

Something from a Chinese source - the Six Secret Teachings:

http://en.wikipedia.org/wiki/Six_Secret_Teachings

King Wu asked Tai Gong: "What about battle chariots?"
Tai Gong replied: (...) In general, in chariot battles, there are ten types of situations on which demise is very likely and eight on which victory can be easily achieved."
King Wu asked:"What are the ten fatal situations like?”
Tai Gong replied:”If after advancing, there is no way to withdraw, this is a fatal terrain for chariots.
Passing beyond narrow defiles, to pursue the enemy some distance, this is terrain which will exhaust the chariots.
When the land in front makes advancing easy, while that to the rear is treacherous, this is terrain that will entrap the chariots.
Penetrating into narrow and obstructed areas from which escape will be difficult, this is terrain on which the chariots may be cut off.
If the land is collapsing, sinking, and marshy, with black mud sticking to everything, this is terrain which will ‘labor’ the chariots.
To the left is precipitous while to the right is easy, with high mounds and sharp hills. This is terrain contrary to the use of chariots.
Luxuriant grass runs through the field, and there are deep, watery channels throughout. This is terrain which thwarts the use of chariots.
When the chariots are few in number, the land easy, and one is outnumbered by enemy infantry, this is terrain on which the chariots may be defeated.
To the rear are water filled ravines and ditches, to the left deep water and to the right steep hills. This is terrain on which chariots are destroyed.
It has been raining day and night for more than ten days without stopping. The roads have collapsed so that it is not possible to advance or to escape to the rear. This is the terrain that will sink the chariots.
These ten are deadly terrain for chariots. Thus they are the means by which the stupid general will be captured and the wise general will be able to escape."
King Wu asked:"What about eight conditions of terrain that result in victory?"
Tai Gong replied:"When the enemy’s ranks - front and rear - are not yet settled, strike into them.
When their flags and pennants are in chaos, their men and horses frequently shifting about, then strike into them.
When some of their officers and troops advance while others retreat; when some move to the left, others to the right, then strike into them.
When their battle array is not yet solid, while their officers and troops are looking around at each other, strike them.
When in advancing, they appear full of doubts, and in withdrawing they are fearful, strike them.
When the enemy’s whole army are suddenly frightened, all of them rising up in great confusion, strike into them.
When you are fighting on easy terrain and twilight has not ended, strike into them.
When, after traveling far, at dusk they are camping and their whole army are terrified, strike into them.
These eight situations constitute conditions in which the chariots will be victorious.
If the general is clear about these ten fatal situations and eight situations where victory is almost certain, then even if the enemy surrounds him on all sides - attacking with one thousand chariots and ten thousand cavalry from the front and the flanks - he will invariably be victorious."
"Excellent!" said King Wu.

King Wu asked Tai Gong: "When chariots and infantry engage in battle, one chariot is equivalent to how many infantrymen? How many infantrymen are equivalent to one chariot? When cavalry and infantry engage in battle, one cavalryman is equivalent to how many infantrymen? How many infantrymen are equivalent to one cavalryman? When chariots and cavalry engage in battle, one chariot is equivalent to how many cavalrymen? How many cavalrymen are equivalent to one chariot?"
Tai Gong replied: "Chariots are the wings of the army, the means to penetrate solid formations, to press strong enemies and to cut off their flight. (...) after the masses of the army have been arrayed in opposition to the enemy, when fighting on easy terrain, the rule is that one chariot is equivalent to eighty infantrymen, and eighty infantrymen equal to one chariot. One cavalryman is equivalent to eight infantrymen; eight infantrymen is equivalent to one cavalryman. One chariot is equivalent to ten cavalrymen; ten cavalrymen is equivalent to one chariot.
The rule for fighting on difficult terrain is that one chariot is equivalent to forty infantrymen, and forty infantrymen are equivalent to one chariot. One cavalryman is equivalent to four infantrymen; four infantrymen are equivalent to one cavalrymen. One chariot is equivalent to six cavalrymen; six cavalrymen are equivalent to one chariot.
Now chariots and cavalry are the army’s strong weapons. Ten chariots can defeat one thousand men; one hundred chariots can defeat ten thousand men. Ten cavalrymen can drive off one hundred men, and one hundred cavalrymen can drive off one thousand men. These are the approximate numbers."
King Wu asked: "What are the numbers for chariot and cavalry officers and their transformation?"
Tai Gong replied: "For the chariots - a leader for five chariots, a captain for ten, a commander for fifty and a general for one hundred.
For battle on easy terrain five chariots comprise one line. The lines are forty paces apart, the chariots from left to right should be ten paces apart, with detachments sixty paces apart. On difficult terrain the chariots must follow the roads, with ten comprising a company and twenty a regiment. Front to rear spacing should be twenty paces, left to right six paces, with detachments thirty-six paces apart. If they venture of the road more than two li in any direction, they should return to the original road.
As for the number of officers in the cavalry: a leader for five men; a captain for ten; a commander for one hundred; a general for two hundred.
The rule for fighting on easy terrain: Five cavalrymen will form one line, and front to back their lines should be separated by twenty paces, left to right four paces, with fifty paces between detachments.
On difficult terrain, the rule is front to back, ten paces; left to right, two paces; between detachments, twenty-five paces. Thirty cavalrymen comprise a company; sixty form a regiment. For ten cavalrymen, there is a captain. In action, they should not move out of the range of one hundred paces, after which they should circle back and return to their original positions."
"Excellent!" said King Wu.

And a further fragment from the Six Secret Teachings about chariots:

"(...) As for the basic numbers when employing the army, if commanding ten thousand armed soldiers the rules for [the various types of equipment and their] employment are as follows.
Thirty-six Martial Protective Large Fu-hsu Chariots. Skilled officers, strong crossbowmen, spear bearers, and halberdiers - total of twenty-four for each flank [and the rear]. The chariots have eight foot wheels. On it are set up pennants and drums which, according to the Art of War, are referred to as 'Shaking Fear.' They are used to penetrate solid formations, to defeat strong enemies.
Seventy-two Martial-Flanking Large Covered Spear and Halberd Fu-hsu Chariots. Skilled officers, strong crossbowmen, spear bearers, and halberdiers comprise the flanks. They have five foot wheels and winch-powered linked crossbows which fire multiple arrows for self protection. They are used to penetrate solid formations and defeat strong enemies.
One hundred and forty Flank-supporting Small covered Fu-hsu Chariots equipped with winch-powered linked crossbows to fire multiple arrows for self-protection. They have deer wheels and are used to penetrate solid formations and defeat strong enemies.
Thirty-six Great Yellow Triple-linked Crossbow Large Fu-hsu Chariots. Skilled officers, strong crossbowmen, spear bearers, and halberdiers compromise the flanks, with 'flying duck' and 'lightning shadow' arrows for self-protection. 'Flying duck' arrows have red shafts and white feathers, with bronze arrowheads. 'Lightning's shadow' arrows have green shafts and red feathers, with iron heads. In the daytime they display pennants of red silk six feet long by six inches wide, which shimmer int he light. At night they hang pennants of white silk, also six feet long by six inches wide, which appear like meteors. They are used to penetrate solid formations, to defeat infantry and cavalry.
Thirty six Great Fu-hsu Attack Chariots. Carrying Praying Mantis Martial warriors, they can attack both horizontal and vertical formations and can defeat the enemy.
Baggage Chariots [for repelling] mounted invaders, also called 'Lightning Chariots.' The Art of War refers to their use in 'lightning attacks.' They are used to penetrate solid formations, to defeat both infantry and cavalry.
One hundred and sixty Spear and Halberd Fu-hsu Light Chariots [for repelling] night invaders from the fore. Each carries three Praying Mantis Martial knights. The Art of War refers to them as mounting 'thunder attacks.' They are used to penetrate solid formations, to defeat both infantry and cavalry... [continues to other equipment that has nothing to do with chariots] ..."

And from another Ancient Chinese source - Wuzi attributed to Wu Qi (aka Wu Ch'i):

http://en.wikipedia.org/wiki/Wuzi

Marquis Wu asked: "In general are there methods for taking care of the chariots and cavalry?"
Wu Ch'i replied: "Now the horses must be properly settled, with appropriate grass and water and correct feeding so as to be neither hungry nor full. In the winter they should have warm stables, in the summer cool sheds. Their mane and hair should be kept trimmed and their hooves properly cared for. Blinders and ear protectors should be used so as to keep them from being startled and frightened. Practice their galloping and pursuit, exercise constraint over their advancing and halting. Men and horses must be attached to each other; only thereafter can they be employed. "
"The equipment for the chariots and cavalry - such as saddles, bridles, bits, and reins- must all be complete and durable. Normally, the horses do not receive their injuries near the end of the battle but invariably they are injured at the start. Similarly, they are not injured so much by hunger as by being overfed. When the sun is setting and the road long, the riders should frequently dismount for it is better to have the men weary than to overlabor the horses. You should always direct movements so as to keep some strength in reserve against the enemy suddenly turning on us. Anyone who is clear about this can traverse the realm without hindrance."