Is a person facing court martial entitled to a lawyer?

Yes. All military defendants (technically "accused") are entitled to be represented by a military defense counsel at no cost. (In fact the military began to provide defense counsel long before civilian criminal courts were required to provide them.)

Military defendants are also entitled to retain a civilian lawyer to represent them at their own expense. Civilian counsel who practice military law are often far more experienced, both in military and trial practice matters, than the free military counsel the service provides them. Civilian counsel also are free of the real pressures and constraints that sometimes makes it difficult for a lawyer in the military to provide the same intensity or type of representation.