Editing Union army (section)

===Bureau of Military Justice===
{{main|Judge Advocate General's Corps, United States Army}}
An office of the [[Judge Advocate]] had existed in the US Army since its founding, consisting at the start of the Civil War of a single officer with the rank of major and small civilian clerical staff in Washington.  It was not until after the war began however that Congress formally authorized the appointment of a [[Judge Advocate General]] (JAG) and creation of the Bureau of Military Justice, a [[de facto]] department and forerunner to a true Judge Advocate General's Department.  The principle functions of the JAG included conducting [[Courts-martial of the United States|courts-martial]] and [[inquiry|inquiries]]; codifying the [[law of war|laws of war]] and the [[Uniform Code of Military Justice|military laws of the United States]]; reviewing the records of courts-martial, military commissions and inquiries; and asserting the jurisdiction of military commissions over civilians in times of war.<ref name="Newell98">Newell & Shrader, p. 94-98</ref>

To meet the demands of a vastly larger army, Congress authorized in July 1862 the appointment of a JAG with the rank of colonel and for President Lincoln to appoint a judge advocate of volunteers with the rank of major for each army in the field.  These judge advocates were to advise commanders on legal issues, prosecute offenses, and review and maintain the records of courts-martial and other proceedings in the field.  A year later, Congress legislated the creation of the Bureau of Military Justice, gave it an [[appellant]] function, and authorized the JAG to head it as a brigadier general alongside an assistant JAG with the rank of colonel.  With these authorizations came a small increase in the size of the clerical staff assisting the JAG.<ref name="Newell98"/>

During the war the JAG and his subordinates were able to satisfactorily handle the increased volume and complexity of legal matters that came with the exponential growth of the army.  Among their most important accomplishments was the creation of the [[Lieber Code]] and, for the first time, collecting all precedents, decisions and opinions which had become US military law into a single digest and publishing it in early 1865.  One of the most controversial issues associated with the bureau was the use of military commissions to try civilians, an issue which would not be settled until ''[[Ex parte Milligan]]'' was decided in 1866.<ref name="Newell98"/>

;Leadership
The Civil War began with brevet Major [[John F. Lee]] serving as the judge advocate of the army until September 3, 1862, when [[Joseph Holt]] was formally appointed as JAG.  Holt played an important parts in helping to expanding the office of the JAG and oversaw some of the most important and sensitive trials of the war.  However Holt also made many enemies while JAG and was severely criticized for his handling of the [[Assassination of Abraham Lincoln#Conspirators' trial and execution|trial of President Lincoln's assassins]].<ref name="Newell98"/>