Quoting Chananya Weissman:
Note: The following Torah teaching is for educational purposes, and is not a call to action.
Although a casual reader of Tanach or a Kara’ite will inevitably get this wrong, like so much else, King David had legitimate reason to execute Uriah the Hittite for treason. However, for reasons of personal expediency, he chose to orchestrate Uriah’s death on the battlefield in a way that would appear as a tragic but ordinary event (Shmuel II 11). In this David acted improperly (see Shabbos 56a).
David sent a letter to his trusted general Yoav (ironically in the hands of Uriah himself) instructing him to send Uriah into the heat of battle, and then suddenly pull back the troops, leaving Uriah exposed. Uriah would need a miracle to survive this death trap — a greater miracle than usual in times of war — and such a miracle was not forthcoming. The plan was successful. Uriah, one of the great warriors of the Jewish people (see Divrei Hayamim I 11:41), was killed.
This much is fairly common knowledge, but what happened next is not widely known. Chazal spell it out for us in several places in Midrash (see Bamidbar Rabba 23:13 and Tanchuma Masei 12):
נתקבצו כל ראשי החילים על יואב להרגו
All the heads of the soldiers gathered against Yoav to kill him.
Of course they did. They weren’t stupid. They understood that the bizarre event leading to Uriah’s death was not the product of an intelligence failure, incompetence, a perfect storm of unfortunate coincidences, or expert planning on the part of the enemy. It was a deliberately orchestrated death trap.
Furthermore, whether or not they could fathom a motive or accept it had no bearing on the reality staring them in the face. The crime had clearly been committed either way.
The heads of the soldiers did not decide that now wasn’t the time to ask questions, and that an investigation could be conducted after the war was finished. That would be ludicrous and intolerable. A treasonous general would not be allowed to lead them one moment longer, nor would justice be delayed. The blood of a Jewish soldier sent to die for nothing would be swiftly avenged.
Chazal tell us that Yoav showed them the letter from King David, and his life was spared. Although Chazal don’t elaborate, it is clear that showing them the letter was more than a defense of “I was just following orders”. That would hardly have saved his skin. If anything, those who gave the orders would have been dealt with as well. Rather, the heads of the soldiers must have ascertained that Uriah was guilty of rebelling against King David, which justified Yoav in carrying out the instructions, even though the manner in which Uriah was eliminated was improper.
(Indeed, David openly lamented Yoav’s betrayal in sharing the letter, one of several crimes Yoav committed against David. This is not to say that Yoav should have martyred himself to cover for David, but Yoav’s pattern of vigilante behavior, noted in the same Midrash, renders sharing the letter an act of betrayal as well. Tellingly, Chazal hold Yoav liable for this, and not for carrying out the instructions to have Uriah killed, for which only David is held accountable.)
Were it not for the technicality of Uriah’s own guilt, one of the greatest generals in Jewish history would have been unceremoniously lynched — irrespective of his impressive track record, his value to the Jewish people, or any rationalizations about how many lives he might save in the future if his own life was spared.
None of the heads of the soldiers made any such calculations.
Of course not! A Jewish soldier was sent into a death trap! And they knew what to do about it. End of story.
I agree with the “Note”. Also, I should note that they (surprisingly) took Uriyah’s military ability into account; he was not a lowly soldier (full quote: נתקבצו כל ראשי החילים על יואב להרגו שהיה ראש הגבורים שכך כתיב בו (שם כג) אוריה החתי על שלשים ושבעה).