Improved Two-Weapon Fighting

Two-Weapon Fighting (PH) , DEX 17, base attack bonus +6,

In addition to the standard single extra attack you get with an off-hand weapon, you get a second attack with it, albeit at a – 5 penalty (see Table 8-10, page 160).

Without this feat, you can only get a single extra attack with an off-hand weapon.

A fighter may select Improved Two-Weapon Fighting as one of his fighter bonus feats. A 6th-level ranger who has chosen the two-weapon combat style is treated as having Improved Two-Weapon Fighting, even if he does not have the prerequisites for it, but only when he is wearing light or no armor (see page 48).

You are an expert in fighting two-handed.