Disclaimer: I am not a historian, however I am a naval officer with an interest in the history of naval warfare.

The story of Capt McVay is a challenging story to answer the exact reasons for being the only US Commanding Officer court-martialed for loss of a ship in enemy action - although there is speculation as to why, which have varying levels of trustable accuracy.

First, let's discuss the role of a Commanding Officer, and therefore if there was any legality behind the court-martial of Capt McVay.

As an important note, while 49 of 50 US states follow Common Law based of precedent, the Uniform Code of Military Justice acts less on precedent of Common Law and more on protocol of Civil Law. While in Common Law courts, there would be an argument of lack of precedence to support these charges; under Military Law, provided you meet all elements of a charge, a conviction can be met - the acceptance of this, and punishment awarded is then up to the Presiding Officer of the Court-Martial.

The position of Commanding Officer of a ship has long had a position of absolute authority, and absolute responsibility. The origins of a CO wielding absolute authority goes as far back as Sir Francis Drake ordering the execution of Thomas Doughty in 1578 during a circumnavigation sailing.

Moreover, in terms of the incident’s larger significance, the execution of Doughty by Drake is a watershed moment in maritime history, and a crucial one for the issues explored in this article. Drake’s killing of his one-time friend imposed for the first time the absolute authority of one individual as sole master of the ship. As John Cooke commented in his “Narrative,” when the fleet left England “Francys Drake, John Winter and Thomas Doughtie” were “eqwall companyons and frindly gentlemen” (Penzer 142; Kelsey 98). Yet by executing Doughty so ruthlessly, Drake, the “tarpaulin officer,” (i.e. a sea-bred superior officer) categorically established his chain of command over his social superiors, the gentlemen officers (i.e. elite military officers appointed to command).

This absolute authority of the CO was questioned at the time, both in trial, and among the elite in England at the time - however, since then, the CO of a ship has been afforded near-absolute authority. Which goes to reason that the man who wields absolute authority, also retains absolute responsibility.

The history of taking a naval commander to Court-Martial has also been around for centuries - historically known examples being the Courts-Martial (and subsequent execution) of Lt Baker Phillips RN and Adm John Byng RN for a breach of the 12th Articles of War - for striking colours (Phillips) and retreating to Minorca (Byng)

The 12th Article of War read as follows: "Every person in the fleet who, through cowardice, negligence or disaffection, shall in time of action withdraw, or keep back, or not come to the fight or engagement, or shall not do his utmost to take or destroy every ship ... [or to] assist all and every of His Majesty's ships, or those of allies, which it shall be his duty to assist and relieve; every such person so offending and being convicted thereof by the sentence of a court-martial shall suffer death or such other punishment as the circumstances of the offence shall deserve and the court-martial shall judge fit." The final clause was struck from the Article in 1745, eleven years before Byng's trial.

Lt Phillips' case is important here, as he was only the Commanding Officer at the time when the Captain and Master both died in battle. When Lt Phillips was executed, the Article was amended so it was a mandatory death sentence for all ranks; sentiment at the time being that Phillips was executed due to being a junior rank and that they would not have ordered the execution of a senior officer.

So, it is well established in a historical context, that a Commanding Officer wields absolute authority (Drake) and absolute responsibility (Phillips & Byng). How about in a legal context?

Regardless of legal wrangling, a commanding officer’s responsibility, and his accountability, are absolute in matters that affect the safety of his ship. This tenet is founded in Section 5947 of Title 10, United States Code, which states: “All commanding officers . . . in the naval service are required . . . to take all necessary and proper measures, under the laws, regulations, and customs of the naval service, to promote and safe-guard . . . the physical well-being, and the general welfare of the officers and enlisted persons under their command or charge.”

Now, why was Capt McVay the only CO to appear at a Court-Martial for the loss of his ship?

This is where it becomes very speculative, because the lack of other courts-martial go without an argument. Capt Toti, USN (rtd.) suggests that there is sufficient legal reasoning for a CO to be court-martialed for just about any offence, as their responsibility is absolute - whether or not they could have done anything to avoid disaster is irrelevant; this is seen to this day with COs being fired for events which happen outside their control - USS Fitzgerald, collided while the CO was asleep in his cabin.

Capt Toti posits that McVay was court-martialed due to the American public being outraged at the loss of 800 American sailors in the waning stages of the war. Therefore the matter was investigated following the normal channels: a court of inquiry recommended court-martial, Adm Nimitz disagreed and issued a reprimand, Adm King then overruled Nimitz and ordered a court-martial.

Why the court of inquiry recommended a court-martial is unknown, as opposed to the other 380 sinkings of WWII; however it may have been due to this particular sinking having a higher profile than the others due to the high number of perished sailors and the timing of the sinking in the final weeks of the war.

Edit: I've found the summary for McVay's Court of Inquiry. For those unaware - a Court of Inquiry is done as a fact-finding mission primarily, it is not a legal court in the likes of a Court-Martial (ie a Court of Inquiry cannot convict, it can only make recommendations).

From reading the findings, the recommendation to convene a Court-Martial for Capt McVay (with respect to the charge he was ultimately convicted for) appears to rely solely on the failure to zig-zag at the time of sinking. This is interesting, as the Court itself admits that zig-zag manoeuvres would have been ineffective near a submarime anyhow - the submarine commander famously testified this at the ensuing Court-Martial. However, it was a breach of naval policy/doctrine at the time, despite no longer being relevant.

As for Adm King's recommendation for a court-martial, Richard Newcomb in his book Abandon Ship, wrote that Capt McVay's father (Adm McVay) reprimanded King (then a junior officer) for sneaking women aboard the ship while Adm McVay was in command. Adm McVay suggested that it was an act of revenge from King to order a court-martial for McVay's son when he had the chance. This, however, is not substantiated outside of Adm McVay's personal belief of King.

I won't try to suggest whether or not it was common for familial backlash towards an ex-CO after a sinking, as I haven't found any media of the day suggesting the deep public outrage at the sinking.

To summarise, however - there was historical precedent behind a CO being court-martialed for the loss of a ship, this being based on the tradition that a CO has absolute authority, and therefore absolute responsibility, on their vessel. This is further placed into US statute that deems the CO responsible for anything that happens on their ship. Therefore, his court-martial had legal ground; although there is reason to argue his conviction was not in the interests of justice. He remained the only CO to be convicted for the sinking, until it was overturned in the Clinton Administration - it is most likely that he received a court-martial owing to the timing of his sinking being at the very end of WWII and out of a traditional battleground, as opposed to the vast majority of the remaining sinkings.

(Sorry if this delves too deep into the history behind COs retaining absolute authority and responsibility - I find it to be relevant and interesting, though it may not have answered your question in the way you intended)

Sources

Penzer, N. M., ed. The Word Encompassed and Analogous Contemporary Documents Concerning Sir Francis Drake’s Circumnavigation on the Globe. New York: Cooper Square, 1969.

Kelsey, Harry. Sir Francis Drake: The Queen's Pirate. New Haven: Yale UP, 1998.

Jowitt, Claire. The Hero and the Sea: Sea Captains and Their Discontents, 2017.

Toti, William. Capt, USN (rtd.) The Legacy of USS Indianapolis