Question: Did the military industrial complex play a role in LBJ's decision to increase America's involvement in Vietnam?
I would argue yes. As we saw in the second gulf war there are generally many factions which move a country such as the United States to war. A chorus of factions which each find different intermingled reasons to support the movement towards war. That's also how it was in Vietnam. Some of the primary reasons given which were used to promote that war were:
- Creating a strong anti communist pillar in south east Assia to further secure the region from Communist expansion after the current threat was dealt with.
- The Domino Effect, Stopping the chain reaction of destabilization and fall of countries around the world into Communism. This phrase represents both one of the biggest ideologies which moved the nation to war, and one of the countries biggest ideological mistaken beliefs. In reality North Vietnam's victory wasn't the first domino to fall as this theory predicts but exactly the kind of nation the US was fighting to put in place. In 1979 they would fight and win a war against China to stop China's expansion in the region. In the early 1980's Vietnam would fight and defeat the pro Chinese communist Khmer Rouge; and then they would withdraw and support the United Nations governing of Cambodia in the aftermath.
- Defending Freedom of Navigation which has been a US Navy mission around the globe since Thomas Jefferson created the US Navy. For this faction N. Vietnam's attack on the USS Madox in international waters(gulf of tonkin) represented an act of war and was in and of itself justification of the war. The resolution which enabled the Johnson Administration to wage war in Vietnam on the scale he did bares the name of this attack, Gulf of Tonkin Resolution; only that attack is now suspect and likely never occurred, according to then Secretary of Defense Macnamara in his book "Fog of War.
- Unlike in Korea, in Vietnam the United States military was ready for the fight. Investments by the Eisenhower, Kennedy Administrations since Korea had created a well funded and large US military which emboldened US policy makers. When North Korea invaded South Korea in Jun 25, 1950 the US Army wasn't ready. In June of 1950, the US military was a shadow of the force which had fought Germany and Japan in 1945. Most of it's divisions had been disbanded, the once vast navy had been mothballed. It's funding had been seriously curtailed. It's post WWII mission abroad was not clearly defined in the eyes of policy makers. None of this was the case in Vietnam. Yes the Military Industrial Complex which made the US the arsenal of democracy in WWII had been recreated on a somewhat smaller scale in order to allow the Country the capability to engage and defend US interests abroad. A component of the voices which moved the country to war in Vietnam saw it as just the next battle field against communism and they were supporters and emboldened by the Military Industrial Complex which President Eisenhower had warned the country against in his farewell address.
From the Question:
In particular, he was told early on that the North could commit enough soldiers to make the war unwinnable for the U.S. He still persisted with bombing the North, and sending ever more Americans to Vietnam.
The Vietnam war wasn't lost on the battlefield. North Vietnam could never have committed enough soldiers to make the war unwindable for the U.S. When North Vietnam at times tried to fight a conventional war against the United States, it was when the United States forces were most effective and N. Vietnamese forces lost their largest forces in the field (Tete Offensive, Khe Sanh). N. Vietnam won the war on five primary points.
- The United States and South Vietnam never invaded North Vietnam for fear of inviting direct Soviet involvement and potentially nuclear war and war in Europe. This war policy removed any possibility of a victory due to military action for the United States. The US had the men and capabilities to invade the N but would not do it. This seeded the initiative to the North, and committed the US military to a strategy which would require prolonged domestic popular and political support measured in decades for a war in which no vital American interests were present.
- North Vietnam benefited greatly from the Johnson and Nixon administrations policy of running the war from 9000 miles away. Objectives, ground campaigns, strategies and even bombing targets on a daily basis were decided on, not in theatre but in Washington. This was a significant handicap for the U.S. war effort.
- Recognizing the United States was recycling it's strategy from the Korean War. Playing for a stalemate and not a win, North Vietnam adopted their own strategies to make such a cost and commitment unsupportable.
- Using asynchronous warfare to harass and bleed the U.S. and South Vietnamese forces was to North Vietnam's great advantage. When North Vietnam tried to fight a conventional war several times during the conflict and the results were disastrous for them. They were most effective and ultimately owed their overall success in the decision to fight a gorilla war, one with smaller units acting less predictably to harass their enemy.
- N. Vietnam recognizing and engaging in the political war brewing in the US over the war. This was a war where propaganda, imagery and public perception played an oversized role. N. Vietnam engaged in this growing unrest and was successful at it.
Question: Update: As @BenCrowell points out, JFK seemed to know that war would be unwinnable and wasn't interested in a pull-out either. Whether LBJ's policy views were different from JFK's is important, of course, but is secondary to whether the MIC was pulling the strings during LBJ's term. I'd like to know the answer to that as definitively as public records allow us to know.
Kennedy was a very young man when he became president compared to his predecessors. He was the first American President born in the 20th century. He was the first American President not in leadership during WWII. He supported many progressive actions at home namely civil rights, civil liberties, overhauling immigration, space policy, and generally a bold and exciting vision for the country. All these things made him popular with the countries progressives and young people which in later years would form the backbone of the anti Vietnamese war movement.
After Kennedy's death, these Kennedy supporters would argue that Kennedy would have kept us out of Vietnam and not have made the same mistakes in judgement and hubris as the Johnson administration. Perhaps, but I would also note that Kennedy was a foreign policy hawk. The advisors who moved Johnson to war in Vietnam:
- Maxwell Taylor,
- Dean Rusk,
- Robert McNamara,
- the National Security Council
Were put in place by Kennedy. Johnson inherited them. McNamara was recruited by Kennedy out of the auto industry. It's much more likely that Kennedy would have taken the same path recommended by these men which Johnson took, after all they were Kennedy's team.
Question:
Is there any evidence showing that the military industrial complex swayed LBJ's decisions?
It's really a chicken or the egg discussion. The MIC was created to give the country a better more creditable military option in confronting Soviet expansion. It was created with significant bi-partisan political support by American policy makers, and it was ultimately used for that purpose. Yes hundreds of billions of dollars were in the mix, and yes corruption and self interest is present in any governmental effort which see's that kind of financial and political commitment. Ultimately what fueled the creation of the MIC was a real and broad bipartisan palpable fear of soviet expansion and what was believed to be an existential need to confront that expansion. Did the MIC fuel and support these feelings in a creditable and substantive way. Yes. Military leaders were in the news nightly espousing the need for American involvement. Corporate spokesmen would right and expose support for hawkish policy by advisors and government policy.
The fear of the Soviet Union dominated America's foreign policy from the fall of China in 1947 to the fall of the Berlin Wall in June of 1990. It's ultimately that fear which drove everything including the expansion of the Military Industrial Complex.
Path to War (2002) starts with LBJ's election victory in 1964 and shows him making somewhat irrational decisions, against the well-argued advice of some of his advisers, leading to the War in Vietnam.
The best documentaries I've seen on the Vietnam war were

Vietnam War With Walter Cronkite
.

The Vietnam War with Ken Burns
And if you don't have a week to view these half a day's comprehensive documentaries on the subject. then this latest documentary by one of the nation's most famous hawks of that time, I found thought provoking and excellent. Also a best seller in Vietnam where McNamara travels to decades after the war was over to meet with and interview his counterparts in the war.

Fog of War, by Robert McNamara