D was 13 when he moved to the United States from South Korea in 1982. In the 35 years, he has spent in the country, D has never returned to South Korea. He did not become a United States citizen, living instead as a lawful permanent resident. D ran a lawful business but also engaged in some illegitimate activity. In 2008, a confidential informant told federal officials that D had sold the informant approximately 200 ecstasy pills and two ounces of hydroponic marijuana over the course of eight years. The officials obtained a search warrant for D’s house, where they found 88 ecstasy pills, three Valium tablets, $32,432 in cash, and a loaded rifle. D admitted that the drugs were his and that he had given ecstasy to his friends. D was indicted for intent to distribute and retained an attorney and entered into plea discussions with P. The attorney advised D that going to trial was “very risky” and that, if he pleaded guilty, he would receive a lighter sentence than he would if convicted at trial. D repeatedly asked him whether he would face deportation as a result of the criminal proceedings. The attorney told D that he would not be deported as a result of pleading guilty. D accepted the plea and the District Court sentenced him to a year and a day in prison, though it deferred commencement D’s sentence for two months so that Lee could manage his restaurants over the holiday season. D had pleaded guilty to what qualifies as an “aggravated felony” under the Immigration and Nationality Act, and a noncitizen convicted of such an offense is subject to mandatory deportation. D filed a motion under 28 U. S. C. §2255 to vacate his conviction and sentence, arguing that his attorney had provided constitutionally ineffective assistance. The attorney acknowledged that if he had known D would be deported upon pleading guilty, he would have advised him to go to trial. A Magistrate Judge recommended that D’s plea be set aside and his conviction vacated because he had received ineffective assistance of counsel. The District Court denied relief. The District Court concluded that D’s counsel had performed deficiently by giving improper advice about the deportation consequences of the plea. It found in light of the overwhelming evidence of D’s guilt,” D “would have almost certainly” been found guilty and received “a significantly longer prison sentence, and subsequent deportation,” had he gone to trial. Thus D could not show he was prejudiced by his attorney’s erroneous advice. The District Court granted a certificate of appealability. The Court of Appeals affirmed. D was required to show “a reasonable probability that, but for counsel’s errors, he would not have pleaded guilty and would have insisted on going to trial.” D had “no bona fide defense, not even a weak one,” so he “stood to gain nothing from going to trial but more prison time.” The Supreme Court granted certiorari.