Impel is a Spear strategy.
As the war between Cao Cao and Dong Zhuo raged, Han Zhong was taken to secure a foothold on the tyranny's forces. On the brink of Dong Zhuo's defeat, Liu Yan finally decides to ally with Dong Zhuo, sending several forces to take Han Zhong. However, their forces were weak and were non-equipped with hiking material. In result, Liu Yan was forced to retreat as his forces kept on falling off cliffs. Cao Cao decided to reasearch as an insult to Liu Yan;s failiure even further by upgrading their Spear attack "Thrust" into "Impel".
Officer ATP: B
Research: Adept March
Game Description: Push troops off cliffs.
Additional info: This does more damage than Thrust if you use it near cliffs. If you Impel a unit that has a cliff directly behind it, the backline units are thrown off the cliff, dealing more damage. There is a 2% chane of throwing the officer off too. However, they only usually get Weakened only.