The Revolt of the Admirals
The Joint Chiefs of Staff were beyond stunned. Technically, what the President did wasn't illegal, but they had directly gone over their heads to launch a nuclear attack. An actual nuclear attack. The diplomatic corps was in a frenzy precisely because of who was incredibly angry: surprisingly, the South Chinese had been outraged, viewing the attack as a permanent blemish on what they thought was rightful ROC territory. The Communists were also enraged, realizing that May Day was picked as the date of the bombing just to tweak the Communists.
The angriest members of the US military were the admirals, led by Admiral Arthur Radford, former commander of the United States Pacific Fleet and Chairman of the Chief of Staffs. Radford had always been opposed to the idea of increasing America's nuclear deterrence while shrinking the rest of the military. Not only was he a strong proponent of American naval power, he was more importantly ferociously opposed to the use of nuclear weapons, viewing them as evil. He had always feared that President McCarthy was unstable and increased the risk of a nuclear conflagration.
Radford had previously given his subordinate on the JCOS, Admiral Daniel V. Gallery a largely open hand to build contingency plans against the President in case he became too erratic. However, Radford himself was less excited on such an approach, feeling that the situation was unsalvagable. With the nuclear attack on North China, the situation became untenable. Alongside other admirals such as Admiral Louis Denfeld, Arleigh Burke, and John Cromellin, the admirals had become united. Many military leaders genuinely feared that the Soviet Union would respond with a nuclear attack on America itself.
They of course, had their man they wanted in charge. A military man who they knew would 1) take the job if offered and 2) loathed McCarthy. They would sell the plan to the other services by claiming that they would put in charge the most popular and well-known military man in America: Douglas MacArthur. This gambit helped push most of MacArthur's former subordinates into joining the cause, including most notably his intelligence man, Charles Willoughby, who had apparently been plotting against McCarthy as well. The two groups quickly combined their efforts.
Buy-in from the Army was somewhat less than-expected, as seen by the refusal of Omar Bradley, Matthew Ridgway, Mark Clark, Lucius Clay, and Dwight Eisenhower to join the plot. However, the plotters still had significant Army buy-in, as represented by General Maxwell Taylor, the former commander of the famous 101st Airborne. In addition, buy-in from the Air Force was slightly more than expected, even though Strategic Air Command had launched the attack. However, Curtis LeMay, the towering figure of SAC, was presumably in some North Chinese POW camp, having been captured in the North Chinese invasion of South Korea, meaning that many troubled Air Force officers felt emboldened to switch sides, especially those who had served under MacArthur in the Pacific.
In addition, luckily for the Admirals, the United States Marine Corps had been folded into the US Navy in 1952, as President Russell searched for extra ways to fund his universal health insurance scheme. As a result, the US Marines were also almost entirely on board. Also incredibly helpful was that most of the founders of the US Special Forces, such as Russell Volckmann and Wendell Fertig, deeply respected MacArthur as the origin of the US Special Forces drew from the liberation of the Philippines in World War II. As a result, they were also largely on board. Interestingly, MacArthur himself was not informed of the plan, as they were afraid what would happen if he said no. However, it seen as unlikely for him to say "no" if the plan was already executed.
On May 2nd, 1957 at roughly 2:30 PM, Washington DC erupted in chaos as the plot materialized. US Marine amphibious tanks, more lightweight than traditional tanks, rolled across the Arlington Memorial Bridge to stunned commuters leaving work early. Paratroopers and Green Berets quickly peppered the city, seizing control of key roads and most importantly, descending on the White House itself. A photograph smuggled out of the city, showing troops parachuting on the White House itself quickly became one of the most iconic photos in American history. Cutting telephone lines, the troops quickly swept the White House, bursting into the Oval Office and detaining an outraged President McCarthy who apparently actually shot two troops dead before he was tackled.
Having seized most of the broadcasting stations in Washington D.C., a panel of generals spoke on television, a technology newly available to most Americans, the Admirals made their case to the nation. Their choice of a spokesman was one of the major leaders in the American Veterans Committee, a major opponent of nuclear proliferation, and generally photogenic speaker all around, the 46-year old actor, Ronald Reagan. Reagan calmly made the case for the coup to America, arguing that the world stood on the precipice of total nuclear annihilation due to a system that concentrated all decision-making process, including that of nuclear war, in the sole hands of one executive, which he derided as the "Imperial Presidency." Reagan argued that the coup was not an unconstitutional act, but rather one designed to restore checks and balances and the original constitutional structure of the three branches of governments. Of course, major military decisions would not be concentrated in the hands of one man: the President, but rather dispersed upon to the top generals of the nation. As for the current political situation, Reagan presented written opinions, prepared by dozens of sympathetic legal scholars, claiming that the Presidential Succession Act of 1947 was actually unconstitutional and simply that there was no good precedent for what ought to be done in this situation, especially as Vice President Kennedy had tendered his resignation to the Admirals. As such, Reagan declared that the "runner-up" to the 1956 elections, Douglas MacArthur, would be appointed Acting President until a provisional presidential election could be held in November, 1958. To further underscore his point, Reagan displayed the trump card of the coup forces, which was surprisingly delivered to them hours before the coup - a personal guarantee from Soviet Premier Laventry Beria, promising that an American administration that entered negotiations to establish "an end to armed hostilities and peaceful trading relations" with the Soviet Union would not be subject to a Soviet nuclear retaliation.
Amazingly, the Admirals, realizing that their actions lacked much democratic legitimacy, made the mistake of not arresting the entire U.S. press corps. Instead, the press was allowed to ask questions to the Admirals directly, and one question would notably set American politics on fire. When asked by a reporter as to the state of President McCarthy, a sheepish admiral noted that he had apparently died in military custody, from appeared to be complications from alcoholism[1], but that they would be willing to participate in any autopsy by an independent party to confirm this. An independent autopsy did in fact confirm that, but the death of President McCarthy would prove to be fuel for dozens of conspiracy theories as to who "really" killed him (suggested answers included the Republicans, the Dixiecrats, JFK, the Admirals, Beria, Chiang Kai-Shek, the Jews, the Freemasons, the Communists, and of course Jewish Communist Freemasons". The US public was rather unconvinced by the official story, something that would explode when a development completely blindsided the Admirals.
Just an hour later, Vice-President John F. Kennedy, broadcasting to the nation from Boston, had a response. Unearthed archives have recently challenged the traditional public understanding of the Coup of the Admirals. Instead, the Admirals actually believed that Vice President Kennedy was part of the plot. Indeed, he had been freely willing to tender them his resignation, written a day before the coup (soon after the nuclear strike). This was because Kennedy had earlier suggested that MacArthur be made the Acting President, just so that the coup could better succeed. Unearthed archives indicate that Kennedy was planning on running against MacArthur in 1958 (and winning). In addition, the "Beria Note" actually came from Kennedy himself, who had unbeknownst to most people, established a secret line of communications with Premier Beria.[2] However, the unexpected death of McCarthy changed this calculus. Vice President Kennedy lambasted the shocked Admirals, claiming that they had murdered McCarthy in order to obtain Kennedy's resignation by coercion. Declaring himself the legitimate Acting President, he called on Americans to resist the new military government, causing public support of the coup to collapse. Kennedy was backed also by many elements of the military, especially in the Army and Air Force, who had rallied behind him.
The final killing blow to the coup came the next day, when the Admirals tried to hold an inauguration that went wrong in every way. Protesters swarmed DC. The troops were ordered not to use lethal force, but this still resulted in widespread brawls across DC. The coup was presented as fait accompli to General MacArthur, who quickly grew to have cold feet. After a 3 AM meeting with Vice President Kennedy, where Kennedy agreed to pursue peace negotiations with the Soviet Union and give the coup planners their day in civilian court (only for the supposed murder of McCarthy), MacArthur gave his first speech as "Acting President" to simply announce that he was not the Acting President, that the forces that had tried to coronate him should immediately stand down to prevent a Second Civil War, and that Vice-President Kennedy had agreed to seek peace with Beria. In his "Old Generals Never Die" speech, MacArthur famously retired from public life, ending the coup alongside his political career.
As a result, the military immediately began to stand down and return to their bases. It was at that point that a ferocious crowd, who insisted that they had "defeated a Communist coup" tried to set upon the soldiers to get "vengeance." Although many soldiers had been brutally lynched, attacking armed US soldiers, especially Marines and Green Berets, proved to be an extremely bad idea, and a mass firefight took place around the White House and on Capitol Hill, causing terrified Congressmen to hide in their offices from the shooting, burning, rioting, and looting. The Smithsonian was famously looted by rioters, who might have not been related to the political struggle, but just random guys from across the Anacostia River who saw an opportunity. DC went up in flames until the next day, as fighting only ended when Vice President Kennedy rolled into DC, calling for an end to the fighting. This almost failed when a disgruntled rioter actually took a shot at President Kennedy. However, the bullet only grazed his cheek. The fighting however, did completely stop when a bleeding Kennedy called for the fighting to end. On that same day, May 4th, 1957, President Kennedy was inaugurated (his cheek was bandaged), battered, but alive. The next day, on May 5th, 1957, President John F. Kennedy, President Zongren Li, and what was left of the North Chinese Politburo declared a cease-fire.
Kennedy, Li, and Beria quickly flew to Melbourne, the site of the final peace settlement that would end the war, perhaps one of the most drama-filled diplomatic events in history. Amusingly, they would use facilities from the 1956 Summer Olympics, which was notably boycotted by both the Western bloc and the Soviet bloc, leading to the most poorly attended Olympic games in history, where Australia had won the most medals, followed by Italy, South Japan, Iran, Ireland, and Mexico.
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[1] Actually OTL, both in date and cause.
[2] OTL, Kennedy had a secret backline to Khrushchev.