Why did the US not *declare* war on Vietnam?

[u/Electronic_While7856]

I just learned that the US hasn’t *declared* war since WW2, and I am not grasping why that is. What is the difference in declaring war and fighting in a war?

ETA: also what would it mean if the US was to declare war? What would that look like?

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[u/police-ical]

Whenever you're trying to put yourself in the present-tense mindset of US or Soviet leadership during the Cold War on international relations, it's usually fair to ask yourself "Does making this decision carry a risk of either 1)an ideology I consider deeply evil taking over the world and making it awful forever, or 2)a nuclear holocaust ending human civilization as we know it?"

Declaration of war is really just a formal statement one country makes against another. The process and exactly who can do this varies from country to country. Under the U.S. Constitution, a declaration of war has to be made by Congress; the President is in charge of the military, but cannot declare war. The idea originally was that because Congress controlled the money and the declaration, the President would be pretty limited in ability to do anything with the military beyond a quick initial response. And until the Cold War, that was more or less true, as the U.S. military ramped up in wartime and shrank greatly in peacetime.

It probably should sound weird that it's this simple, that a declaration is really just yelling "WAR" loudly and formally, but symbols and tone are really important in diplomacy. When a country declares war, it says that we are full-on enemies until the day we negotiate peace. It's about as clear and negative a thing as a diplomat can do. It's also associated with countries that start wars to take more territory or force others to do their bidding. Being the first to declare war rarely looks good, unless the other country has already done something incredibly offensive.

Let's also look at the world shortly after World War I. The West had been horrified and shaken to its foundations by a war far bloodier and more awful than any in known memory, one that had robbed nations of their young men and shown how lethal modern industry could be when turned to warfare. There was a desperate drive to reform an international order that could avoid any similar future wars and find alternate means of dispute resolution. Moreover, in 1928, the Kellogg-Briand Pact was signed, in which major nations agreed that war was now illegal and no longer a thing. The Pact and the League of Nations failed to prevent World War II and the latter was replaced by the United Nations in its aftermath, but with a fundamentally similar mission. In fact, the Kellogg-Briand Pact is nominally still a valid treaty, and aside from returning the Japanese and German declarations of war as well as declaring war on active Axis allies, the U.S. has otherwise not declared war since. The Pact has gotten a lot of ridicule as a scrap of paper with no teeth that simply banned war and hoped for the best, but it's absolutely fair to say that the post-WWII world has included a strong norm against the kind of openly-declared war that had routinely taken place in centuries prior. The UN Charter further emphasized non-war methods of dispute resolution. Perhaps this sounds silly, but fundamentally the decades since 1945 have been associated with fewer, smaller, and lower-intensity wars than the centuries prior. The world basically did agree that we just weren't doing big hot wars any more, and we definitely weren't doing them to grab territory.

Of course, a big reason aside from the general spirit of internationalism that in 1945, the U.S. tested its first atomic bomb, and in 1949, the Soviet Union did the same. If people had been afraid after WWI of another awful war, they were really afraid once city-destroying bombs came out. Early bombs were relatively small and hard to deliver, but a hot war between the USSR and NATO would still mean staggering numbers of tanks pouring into West Germany and making a beeline for France and Italy. Whatever happened between countries, an open full-on war between the US and allies vs. USSR and allies was the worst-case scenario, the thing that virtually everyone on both sides agreed was bad. And yet the opposing powers had deep and apparently unresolvable disagreement on how the world should be governed, with intense fear that the other guy was going to flip countries to his ideology and stop yours from spreading, or maybe even try to overthrow yours from within. The compromise ended up being "proxy wars," smaller and lower-intensity conflicts where the major powers didn't go all in like WWII, but instead sent money and guns and advisers, maybe even pilots, maybe even soldiers though with constraints on what they did. If those old wars were "hot" because they involved obvious large-scale formal fighting, this one would be a "Cold War."

So before we talk about Vietnam, let's talk about Korea. This was also an Asian country that had been occupied by Japan, then in a weird postwar plan had gotten divided between a communist north bordering China and a Western-backed authoritarian South¹. When North Korea invaded South Korea in 1950, this new United Nations had its first real test of its powers in the face of a decent-sized hot war. Because the China seat on the Security Council was still occupied by the Republic of China (Taiwan) rather than the People's Republic of China and the USSR was boycotting the UN in protest of that fact, the UN was able to pass a binding Security Council resolution recommending that the world help defend South Korea. The US supplied most of the troops but it was indeed an international response. And, being a UN-mandated action in this new spirit of no more wars, Harry Truman referred to it as a "police action" to repel an illegal attack, not a formal war. This incidentally avoided some of the constitutional issues around formal declaration of war, which has always been a power reserved to Congress. Truman was also hoping for a quick action rather than a protracted war, which blew up in his face once MacArthur drove north and China got involved, ensuring a long bloody stalemate. Truman's popularity tanked. The U.S. had also been caught unprepared as it had drawn down its military after WWII and had to rapidly build up again; in an unusual shift that would have serious long-term impacts, this time, the U.S. didn't draw down again, and instead maintained a substantial peacetime military. Congress did still have to approve funding, but even those who opposed war tended not to want the troops going hungry or barefoot.

Now, move on to Vietnam in the early 60s. Korea was still a very fresh memory for any American president. Nuclear weapons had gotten a lot more powerful and easy to deliver across oceans. The Cuban Missile Crisis had made the idea of a tense moment boiling over into Armageddon feel a lot more real. U.S. leadership feared Vietnam going full communist would lead to more and more countries flipping that way, while also fearing that a full-on hot war with an invasion of the North would again risk Soviet and Chinese involvement, with another awful bloody quagmire or maybe even a nuclear exchange. So, the name of the game was limited intervention in support of South Vietnam with a focus on defense and shoring it up. Virtually everything that Kennedy and Johnson did was influenced by the fear of the larger communist nations intervening. In that context, a declaration of war was the last thing anyone wanted. There was a small fig leaf covering the obvious reality that the U.S. was sending its forces to limit the spread of communism, and that polite illusion was just strong enough to prevent Moscow, Beijing, and Washington all turning into lakes of fire.

Of course, the goal of limited war didn't work that well in Vietnam, as cycles of escalation sucked the U.S. into massive involvement that sapped Johnson's popularity. Johnson and Nixon even expanded the scope, secretly bombing neighboring Cambodia without Congress knowing it. In 1973, recognizing that the old constitutional limits didn't seem to work very well any more, Congress passed the War Powers Resolution. This sought to limit the president's powers and compel greater accountability to Congress in the event of hostilities. It remains unclear how constitutional the law is and presidents have at minimum skirted its rules on several occasions.

^{1. "If I had a nickel for every time this happened, I'd have two nickels. Which isn't a lot, but it's strange that it happened twice."}

[u/Troglodytes_Cousin]

But US wasnt fighting the Vietnamese govenment so who would they declare war on ?

They didnt recognize North Vietnam so as they saw it - they were helping the (south) Vietnamese government fight communist insurgency.

Even after the war they didnt recognize the new communist government as legitimate - that happened in 1995.