Its well known that Louis defended his title twice for training expenses. The bulk of the gate going to the Army and the Navy relief funds. Can you think of any others who followed suit?
According to Klompton's book, Greb also fought a few times for free but I don't think it were title defences.
I believe Ray Robinson fought for free a few times. In fact I believe one of his fights he donated his purse to two seperate institutions, one of which was my alma mater and hometown university Southern Illinois University.
I recall one of Benny Leonard's opponents, when he was the champ, was going to fight for nothing, the whole purse going to Leonard. Just for a chance to win the title.
I should have specified champs defending their titles for free , my fault, I do recall Robinson donated at least one purse to a worthy cause,but I don't know if his title was on the line.
Bob Montgomery and Beau Jack fought a non title bout in 1944 ,the fight grossed $35,864,900 and it went to war bonds. Jack won the fight.
I was under the impression that both SRR, and Joe L. were in the army together, and both donated fight purses to the American forces.