As incompetent as Haig Dave?
Incompetent enough to win.
Incompetent enough to command the most successful offensive campaign ever fought by the British Army in its entire history.
Incompetent enough to learn and adapt his tactics along every step of the way from command of his first attack at Neuve-Chapelle until the end of the war.

I can think of a whole host of German Generals who would have given their eye-teeth to have been as incompetent as Sir Douglas Haig.

Pershing? Too bloody keen to prove a point, too ignorant to listen to those who'd been facing and overcoming the actual problems over a period of three years, simply a commander with no real command or combat experience. Latter day examples Lucas who was in command of the landings at Anzio, Omar Bradley's refusal of specialist armour for Omaha Beach, Westmoreland in Vietnam who instead of translating and using the intelligence files the French had left had them burned.