What did Gideon base his appeal on?

Gideon based his appeal on the argument that his constitutional right to counsel was violated when he was charged with a felony and not provided with a lawyer. He contended that the Sixth Amendment guarantees the right to free legal representation for defendants who cannot afford an attorney. His case ultimately reached the Supreme Court, which ruled in Gideon v. Wainwright (1963) that the right to counsel is a fundamental right essential to a fair trial, thereby extending the provision of public defenders to state courts.