Duryodhana's overconfidence - Kurukshethra warrior strategy

Duryodhana never started a war until he had all confidence that he can win. What was the reason for that? He felt he had two things.
One the numbers - more than 50% strength in army.
Two the warriors - more than enough to match Pandava warriors.
HOW? Let us look at what lead to Duryodhana's over confidence and down fall..