the Army, Holt oversaw the expansion of military law to include the military prosecutions of citizens who were not in the military service. He crafted the argument to the Supreme Court in Ex Parte Vallandigham, By the time he joined the Army, he believed that the only means to prevent treason from occurring again was to ensure that slavery was abolished for all time, and eventually equal treatment under the law enforced in the South. In 1864, he was promoted to brigadier general. He was the first Judge Advocate General to hold a general's rank. He personally prosecuted the court-martial against Major General Fitz John Porter for crimes of disobedience of a lawful order and misbehavior in front of the enemy. Lincoln also offered Holt the position of Secretary of the Interior that same year and Attorney General later in 1864, but Holt declined both offices. He was one of the many politicians considered for the Republican Vice Presidential nomination in 1864. It went to Andrew Johnson, and Lincoln was re-elected. According to University of New Mexico, School of Law Professor Joshua E. Kastenberg, Holt engaged in political activities that were important for the Union's war efforts, but would not be constitutionally permissible today. For instance, Holt crafted legislation that stripped Union Army deserters of their citizenship. The Supreme Court overturned this legislation in Tropp v. Dulles in 1958. Holt's reasoning for this law was that Copperheads and other pro-slavery southern sympathizers encouraged desertions. Holt also used the Army's power to suppress newspapers as well as oversee the arrest and trial of Congressman Benjamin Gwinn Harris of Maryland who "uttered treasonous statements" in the House of Representatives. Abraham Lincoln assassination On April 14, 1865, Lincoln was assassinated by Confederate sympathizer John Wilkes Booth. Booth's accomplice, Lewis Powell seriously injured Secretary of State Seward, and Vice President Johnson was also targeted. Holt prepared an order for the signature of Johnson for the arrest of Confederate President Jefferson Davis and five other suspects. Booth was caught on April 26, 1865, but killed by Boston Corbett, a soldier who violated orders. As Judge Advocate General of the Army, Holt was the chief prosecutor in the trial of the accused conspirators before a military commission chaired by General David Hunter. Two assistant judge advocates, John Bingham and General Henry Lawrence Burnett assisted Holt. The defendants were George Atzerodt, David Herold, Lewis Powell, Samuel Arnold,