According to The Chronicle of Novgorod, 1016-1471 (hereinafter The Novgorodian Chronicle), a battle between the forces of Novgorodian Rus’ led by Prince of Novgorod Alexander Nevsky on one side, and the Livonian branch of the Teutonic Order on the other side, took place at Lake Peipus on April 5, 1242, and it was called the Battle on the Ice.
According to The Novgorodian Chronicle, the battle took the lives of 400 Teutonic Knights and 50 knights were taken prisoner and delivered to Novgorod. However, the number of the full members (Knight-Brothers) of the Teutonic Order didn't exceed from 100 to 120 knights at the time. Then 60 of them moved to Livonia after the Teutonic Order's Livonian branch was formed in 1237 from the remains of a military order called the Livonian Brothers of the Sword, thus compensating its heavy human losses suffered in its war against the Lithuanians (particularly in the Battle of Saule in 1236).
Contrary to The Novgorodian Chronicle, The Livonian Rhymed Chronicle provides the very different data: 20 brothers dead and 6 brothers taken prisoner. This is not surprising because most of the knights of the Livonian branch led by the then Landmeister (i.e. Provincial Master) Dietrich von Grüningen fought in Courland at the time and simply had no time for any conflicts with Novgorodian Rus’.
Soviet and Russian sources (e.g. a political brochure titled The Battle on the Ice written by Anton Kozachenko and published in 1938) often mention Hermann Balk as a commander of the Teutonic Knights in that battle. However, according to the historical records, the battle took place in 1242, whereas Hermann Balk died in 1239.
The most widespread myth is that the Teutonic Knights were encased in too heavy armor, then the lake's ice couldn't bear their weight and broke under them, and the knights drowned. If so, the ice should have broken under the "lightly armored" Russian warriors rather than under the "heavy" Teutonic Knights, because actually, the Russians' lamellar suits of armor were much heavier than the knights' chain-mails.
Soviet divers searched the whole bottom of Lake Peipus but didn't find any weapons, suits of armor or their parts, or human bones.
In addition, The Livonian Rhymed Chronicle reads, "... the killed ones were falling on the grass." The original text reads, "vielen nider uf daz gras." So, it does not mention any ice. This suggests that the place of the battle and/or a time of year when it took place are wrongly indicated in The Novgorodian Chronicle.
As to the ice itself, the forces of Novgorod and the Teutonic Order were fighting closely, face to face. They didn't stand far apart, throwing their weapons at each other or just shouting insults. If we believed the myth of the broken ice, it would turn out that the ice broke selectively only under the feet of the Teutonic Order's warriors, but not under the feet of the Novgorodian fighters. So, it probably was the sort of ice that had patriotic feelings.