This question might be a bit stupid but i have started to wonder since when did the frontal cavalry assaults, where the knights attacked the enemy line with an intention to ride over them or anything else like this.

was there an evolution of frontal cavalry assaults? Did first occur only on more widespread enemy units or something else like that...

Would a straight cavalry assault be logic in 1250 es?

I just read a cronicle about the Baltic crusades where the crusaders tried to attack the Lithuanians but their cavalry attack failed because the enemy had time to fortify themselves with sleds and was prepeared...

I am no expert on cavalry warfare, but I think the type of frontal assault you described would have been in use from the time cavalry was invented, when appropriate. You see infantry in loose formation without field fortifications and the terrain cooperates, CHARGE!!! The Baltic Crusades are an area of special interest to me. When armed expeditions to Lithuania first started, they may have been relatively easy prey, but the Lithuanians were quick learners. You have to be when you are the object of a Crusade.

We were discussing that subject over at the Schola Gladiatoria forum just a couple of weeks ago. Several people brought up a number of interesting links and bits of information. Check it out here: http://www.fioredeiliberi.org/phpBB3/viewtopi...59e9b8488c.

While no real expert, from what I have gathered, the head on couched lance charge became the standard tactic sometime in the late 11th-112th century.

It should be seen in context with several factors. One is the great increase in availability of armour, making true heavy cavalry a posibility.
Another is the day to day function of the knightly military elite.
Unlike the earlier military leavies that made up the frankish or german shield walls in the 9th and 10th centuries, feudal knights are a standing force in their respective realms. They spend most of their time controlling that terretory from enemies foreign and domestic.
As a result, knights would face forces similar to their own; a handfull of knights backed by militia, or brigands/rebels.

In such a context, the extremely agressive attitude of early medevial chivalry is an advantage. By beeing agressive, they can exploit their mobility and hiting power as individual warriors before the enemy has the chance to respond, and hopefully rout them before resistance is organized.

On a large scale this becomes a lot more tricky. Early medevial armies where made up of local nobles that never practiced together, and a large army is much harder to overwhelm. Especially if that army has a core of professional troops and are on the defensive. (since defence is easier to coordinate than attack).

Since this is most definitely a do-or-die affair, heavy cavalry attacks sometimes go horribly wrong, as in the example that you mention. However, it still works well enough that it remains common at least into the 14th c, and occationally after that as well.