Crittenden continued in the United States military until the outbreak of the American Civil War in 1861, rising to the rank of lieutenant colonel.

In December, Zollicoffer made a tactically questionable decision to move his troops north of the Cumberland River; by the time Crittenden arrived on the scene from his Knoxville, Tennessee, headquarters, it was too late to correct this deployment.

Assigned to command a corps under General Albert Sidney Johnston, Crittenden was arrested on April 1 for being drunk on duty.

He was brother to Thomas L. Crittenden,[1] and he was the firstborn son of John J. Crittenden,[2] who was an influential politician: governor of Kentucky in the late 1840s and early 1850s, United States Attorney General in the administrations of Presidents William Henry Harrison and Zachary Taylor, and a United States Senator.

The regiment was initially slated for garrison duty, but saw active service when the Black Hawk War broke out later that year.

After the end of the Black Hawk War, the 4th Infantry returned to building military infrastructure in the Southern United States, including being stationed for a time in the Arkansas Territory,[8] and in Georgia and Alabama.

[4] Joining the Army of the Republic of Texas, Crittenden participated as a second lieutenant in the 1842 Mier expedition,[10] an incursion by Texian troops into Mexico that was made without orders.

[11] Biographer James M. Prichard considers this to be doubtful, as the tale is not found in survivor accounts of the incident and as the prisoners were blindfolded while drawing the beans, along with the fact that Crittenden had previously been transferred to a hospital.

[13] Released in April 1843,[14] Crittenden was returned to New Orleans, Louisiana, via Vera Cruz and Havana, arriving back in the United States on May 7.

Crittenden was arrested for drunkenness, and tendered a resignation, after which he traveled to Washington, D.C. to plead with the United States Secretary of War.

[11] Additional personality problems had surfaced during the Mexican War; Crittenden nearly participated in a duel, although the confrontation was defused by others.

[16] After a stay at Jefferson Barracks in St. Louis, Missouri, Crittenden traveled across the country to the Oregon Territory in 1849 with the Regiment of Mounted Riflemen.

While serving on the frontier, he fought against Native Americans, including an action against Comanches on January 2, 1861, that brought him national newspaper attention.

Eubank suggests that some of these personality issues could have stemmed from the death of his mother during his adolescence and pressure to fulfill his role as the family's firstborn son.

Southern political leaders known as Fire-Eaters expressed fears that the incoming Republican administration would restrict slavery and support for secession grew in the South.

[22] On the morning of April 12, Confederate military forces opened fire on Fort Sumter in Charleston Harbor; the American Civil War had begun.

[26] Prichard notes that some sources claim that Crittenden was part of a conspiracy to establish Confederate control over the southwestern United States and that he tried to get the men of his regiments to join the Confederacy.

In late October, Davis sent a letter to Crittenden stating that he was considering appointing him to command a Confederate force to claim Kentucky for the Confederacy.

On December 16, Crittenden informed Johnston that he planned to leave with Carroll to join Zollicoffer two days later, but this was delayed by the need to prepare the troops for active service.

[42] By January 18, Union forces commanded by Brigadier General George Thomas were at Logan's Cross Roads, nearing the Confederate camp.

Outnumbered by the combined Union force, Crittenden decided to attack while his opponents were still separated and sent his troops on a night march against Thomas on the morning of January 19.

[50] Crittenden anticipated a follow-up attack from the combined forces of Thomas and Schoepf, and ordered a retreat across the river.

[52] Crittenden's retreat continued all the way to Gainsboro, Tennessee, at which point his army was, in the words of Prichard, "nothing more than an armed mob".

[52] Eubank believes that it is very likely that Crittenden had been drinking to some extent before the battle, although the degree of his insobriety is unclear, while stating that he "clearly was drunk" during the retreat.

Another court of inquiry was opened on September 22, focusing specifically on a charge associated with an anti-drunkenness act passed after Crittenden's arrest.

When he learned that this second trial was also expected to dissolve, he wrote to Confederate Adjutant General Samuel Cooper, questioning why he was being tried in accordance with a law not in effect at the time of the violation.

[57] Cooper decided that since Crittenden was not chosing to actively defend himself against the charges, but was instead basing his defense on a legal technicality, he should be allowed to resign.

The next month, Confederate forces abandoned east Tennessee, and Union Major General Ambrose Burnside moved into the region.

In September, Crittenden led a small force in a series of delaying actions against a Union cavalry advance, which enabled Williams to form a successful defensive line.

[70] The historian Lawrence L. Hewitt states that Crittenden "became a hero among his fellow Kentuckians", as Kentucky culture became more pro-Confederate after the abolition of slavery.