Being caught in double underhooks is a terrible scenario for any grappler or fighter. The most basic defense to this position is to back your legs out, push against the chest, and get to a neutral stance.
In Judo, however, there are some nice counter throws to double underhooks. Immediately locking up with double overhooks, you can begin twisting your opponent’s shoulders to put weight on one foot, then attack that foot with O Soto Gari.
If your opponent resists by pushing into you, stick out your leg like a turnstyle, and use your hips to throw him with Harai Goshi.
Finally, if he resists O Soto Gari but doesn’t commit enough momentum towards you for a Harai Goshi, then you can step out to the side of his left foot, step back in with the left foot facing the right wall, and bring the other leg up and sweep through the inner thigh for a leg-style Uchi Mata.
Check out the video above for demonstrations of all three counter throws: O Soto Gari, Harai Goshi, and Uchi Mata.