One of the reasons that insufficient numbers of National Guard troops were available for immediate response to the Katrina hurricane disaster goes back to the lessons learned by the officer corps from the Vietnam War.
One of the most serious criticisms that military leaders made of Lyndon Johnson's Vietnam War policies was his refusal to call up the reserves. Instead, he relied on the draft to provide sufficient troops for the war. This was part of a political calculation on his part. He was unwilling to create a war fever among the public. Thinking back on the war fever in America after 9/11 and especially before the invasion of Iraq in 2003, it's easy to see why he was reluctant to kindle passions that intense.
He thought moblizing the reserves would have that effect. It's often forgotten now, but during the first two years after Johnson's Americanization of the war in 1965, his policies in Vietnam were criticized more by conservatives than by liberals. This was a continuation of a pattern set in the 1964 presidential campaign, when Republican Barry Goldwater made his own demand for rapid escalation and heavy bombing in Vietnam one of the central issues of the campaign.
The Joint Chiefs of Staff, however, saw the mobilization of public opinion in a more dramatic way as a positive benefit. And they saw a call-up of the reserves as a way to achieve that. In addition, members of the reserve already had prior training and were thought to be better motivated than draftees.
Their experience later in the Vietnam War was widely seen as a validation of the latter assumption. As George Herring wrote in America's Longest War: The United States and Vietnam 1950-1975 (2nd edition; 1986):
The malaise that increasingly afflicted the nation quickly spread to the U.S. armed forces in Vietnam. Until 1969, American GIs had fought superbly. After the initiation of Nixon's troop-withdrawal policy, however, the purpose of the war became increasingly murky to those called upon to fight it, and many GIs became much more reluctant to put their lives on the line. Discipline broke down in some units, with enlisted men simply refusing to obey the orders given by officers. Attacks on officers in time of war were not unique to Vietnam, but "fragging" [assassination of officers] reached unprecedented proportions in the Vietnamization period, more than 2,000 incidents being reported in 1970 alone. The availability and high quality of drugs in Southeast Asia meant that the drug culture that attracted growing numbers of young Americans at home was easily transported to Vietnam. The U.S, command estimated in 1970 that as many as 65,000 American servicemen were using drugs. Nor were the armed services immune from the racial tensions that tore America apart in the Vietnam era, and numerous outbreaks of racial conflict in units in Vietnam and elsewhere drew growing attention to the breakdown of morale and discipline. With obvious pain, old soldier Matthew Ridgway, who had restored the morale of the army in Korea after the firing of Douglas MacArthur, lamented the "grievous blows" that Vietnam had inflicted on his beloved army. (my emphasis)
However, the explanation that these problems resulted in particular from the use of draftees is very questionable, at best incomplete. As Herring says, once withdrawal began and as time dragged on in an inconclusive war, GI's became more and more reluctant to risk being the last one to die for a mistake, to borrow John Kerry's famous phrase. Even apart from that, the particular conditions of fighting a war of that type with the approach used by our infallible military, put extreme stress on the troops in the field.
But that lesson was widely accepted, for better or worse, among the officer corps. Rummy, with his usual diplomatic manner of speaking, gave an illustration of that when he commented that draftees would make inferior soldiers.
In 1968, JCS Chairman Earle Wheeler presented a request to Johnson for an additional 206,000 troops, telling him that without the additional troops possible defeat or at best a protracted stalemate would result. Herring writes that Wheeler may have been genuinely alarmed about the state of matters in Vietnam.
It seems clear, however, that by presenting a gloomy assessment he hoped to stampede the administration into providing the troops needed to rebuild a depleted strategic reserve and meet any contingency in Vietnam. His proposal reopened in even more vigorous fashion the debate [over Vietnam] that had raged in Washington throughout 1967.
The effect of that particular attempt turned out to be the opposite. The huge request prompted Johnson to order his new Defense Secretary Clark Clifford to undertake a thorough review of the US prospects in Vietnam. That review led to Johnson's decision to declare a bombing halt, seek a negotiated settlement and also drop out of that year's presidential race.
(An interest aspect of Wheeler's request was that to justify it, he argued that the US victory in the recent Tet offensive had been "a near thing." The conventional view of that event was that the US decisively won it.)
And as a result of that lesson, the Pentagon sized its forces in such a way that future Presidents would be forced into calling up the reserves. So by the time of the Gulf War in 1991, the Army's policy had the desired effect. Old Man Bush called up the reserves for that war, which proved to be considerably shorter than the one on which his son would embark 12 years later.
Now one of the results of that policy is that the reserves and National Guard are being called up for as much as two years of duty in Iraq.
Which meant that when Katrina struck, something like a third of the National Guard of Louisiana and Mississippi were in Iraq.
And because the long deployments have been hugely unpopular, the use of the reserves has increased public questioning and criticism of the Iraq War, exactly the opposite of the military's expectation. The policy is also turning in on itself, as enlistments and reenlistments in the Guard and reserves are declining in a serious way.
And now the Army is worried that maintaining the current level of forces in Iraq for another year or so will start to lead to morale problems like those experienced in Vietnam.
The big "catch" in the whole plan was that the Army and the other services spent the years since the Vietnam War, and even since the fall of the Soviet Union, preparing to fight Soviet Army Central pouring through the Fulda Gap. Their main strategy for fighting a counterinsurgency war like the current ones in Iraq and Afghanistan was to avoid ever doing it again.