The full quote from Article III, section 3 of the Constitution of the US:
"Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort."

In the context, I think there is a good case that since we are not at war with China, nor have we been for almost 70 years, the actions in question, however contemptible, would not consist of treason. Absolutely, Milley should be punished to the fullest extent of the law, stripped of his rank and discharged dishonorably. Even if the action was correct (which I do not believe it was), that is and should still be the price. Wearing the uniform is a position of trust and service, and you are morally obliged to stand up for the country and service the president. If he gives an immoral order you can disobey it, but the price of putting on the uniform and swearing to obey, is that there are consequences to yourself.

This was not an act of disobedience to immoral commands, this was breaking ranks with the country and exposing divisions or disagreements to outsiders. There is some question as to whether or not members of Congress or Senators communicating with the leaders of potentially hostile nations consists of treason, but when it comes down to it, they are civilians, and there have to be limits on what American civilians can be forbidden from saying. But Milley is not a civilian, he is a serving member of the Armed Forces and under military discipline. Voting against the President is Nancy Pelosi's job. Obeying him promptly and executing his policies is the job of the Chairman of JCS.

If there is a question as to whether or not China need to know something, it is absolutely NOT the decision of ANY uniformed member of the US Armed Forces, nor the job, to convey that information. The lowest ranking service member, facing torture or execution, is obligated not to tell officials of a foreign country anything more than strictly prescribed personal identification data. The standards for generals should be considerably higher. Even the issue of starting or preventing a war is NOT his job! His job is to shut up and shoot if the proper authorities declare war or order and attack, for the very pertinent reason that they are ELECTED OFFICIALS who answer to the voters. Milley does not, and for that reason, cannot and should not EVER be permitted to do ANYTHING that smacks of making policy or exercising the powers reserved in the Constitution for the Executive or Legislature. At best, members of the military should be acting on the President's behalf, not going around him or behind his back. Now if Pelosi is worried about the President's ability to do something like she fears, that's her own damn fault. She's been in Congress since her face looked vaguely human and did nothing to rein in the war-making power ceded to the executive branch since World War Two, and nothing in support of those of her colleagues who introduced bills attempting to reclaim the power to declare war for Congress where the Constitution places it.

What's more, given the authority of Congress over the appointments, assignments and promotions of generals, Pelosi's conversation with him could possibly construed as placing pressure on Milley, given that he supposedly acted on their conversation when she is not in his chain of command.

Because, see, here's the thing - the President might have a good reason (though that probably would not apply to Trump - if anything, he seems like it would have been the generals convincing him to imprudently launch or ill-advisedly not to) for suddenly attacking China, the fact that an election and transition is going on not withstanding. That's why it's his and the State Department's mission to conduct foreign policy and why he's given the authority to conduct military operations for short term periods. It's not the job of a bureaucrat strictly charged with administering the military, to speak for the US and its intentions or policies to foreign powers. I don't see how a general going rogue and "reassuring" the Chinese is supposed to fix their perceptions if they are believing their own propaganda about the US going crazy or where he gets off establishing on his own authority some sort of warning protocol in the event of the US going to war against China.

This is not Trump, or the Deep State swamp hating on him, that results in shit like this. This is a long-running politicization of the apparatus of the state, which is inevitable when those apparatus get excessive. If we were not involved in pointless foreign alliances and deploying our military all over the globe, not to mention fighting generational wars against abstract concepts, we don't need a huge military. Between the outbreak of the War of Independence and the Civil War, back when major European empires had land borders with US territory and hostile designs on the country, we managed to have only two lieutenant generals, George Washington & Winfield Scott. The dangers of a strong army were well-understood at the founding of the country, especially in a nation without a secure authority and focus of loyalty like an established monarchy, and we had the example of France to illustrate it for the dimwitted. Some people whined, as they always do about the dangers of being caught unprepared, and they even went to Grant after the war to suggest the same old thing, that if we had been "ready" to fight, the war could have been ended faster. Grant's reply, despite coming from a man who stood to gain the most by such a policy, was to the effect that if we had a larger professional army in 1860, the South would have had that many more recruits in 1861. The fact that not being in a position to actually do much military in 1914 and 1939 meant that we took relatively few casualties while having a decisive effect on the outcome of both World Wars was also lost on the military fetishists, and we got the Pentagon and Department of Defense, which proceeded to make war in Korea, Vietnam, Cambodia, Grenada, Panama, Iraq, Yugoslavia, Somalia, Afghanistan, Libya and Syria, which, by the way, is one more country than the US declared war on, from 1788 to 1942. 154 years, ten countries, five wars, versus 70 years, eleven countries and zero wars. Because that's what happens when you normalize the military and make it an omnipresent thing - the lines start to blur between military and civilian the way they have blurred between wartime and peace-time. The military becomes political, and politics become militant. Even when you have a guy who obviously spent his days as a field grade officer masturbating to Clear and Present Danger running around babbling his feverish fantasies about standing firm and preventing a coup by Trump, it turns out that he doesn't understand the difference between the roles of elected civilian officials and military officers any better than Trump.