Some troops will fight on in close combat almost regardless of casualties. This can be because they consider themselves to be elite, have taken severe vows to hold their ground in combat or are simply too slow-witted to flee when defeated by superior troops! These troops are referred to as being Stubborn.
During a Break test, Stubborn units use the Leadership. value on their profile. They always ignore Break test modifiers, regardless of how much they lost the combat by. This means, for example, that Stubborn troops with a Leadership value of 8 will only ever break on the roll of 9 or more when making a Break test.