OHHHH.... I know why they dressed as tiger (beside they called themselves the Tiger Warrior).
several thousand years ago some tactician derived a military maze formation called the EIGHTFOLD (related to The Eight Triagrams). This Legendary Maze was said to be unrivaled, whoever master it will triumph every battles. It has eight transformations that changes continuesly to trap the enermy forces. The last time this formation used was in 220-234AD by a man named ZHUGE KONGMING. After KONGMING's dead the formation was lost.
Here is the reason why there was a TIGER DIVISION ( ahahah):
"Heaven, earth, wind, clouds, dragons, tigers, birds, and snakes--what is the meaning of these eight formation?"
"There was an error made by those who transmitted them. The ancients secretly concealed these methods, so they craftily created these eight names. The eight formation were originally one, being divided in eight. Forexample, 'Heaven' and 'Earth' originated in flag designations; Wind and Clouds originated in pennant names. Dragon, tigers, birds,and snakes originated in the distinctions of the platoons and squads. Later generations erroneously transmitted them. If they were cleverly creating formations in the image of animals, why would they just stop at eight?"
that's all we know of the legendary formation.