Forty years ago on this day, Jeffrey Miller, Allison Krause, William Schroeder, and Sandra Scheuer were shot and killed on the campus of Kent State University in Ohio. The bullets which killed them (and wounded nine others) were fired by the Ohio National Guard.

Jeffrey Miller's body (this photo won a Pulitzer Prize).

The Kent State shootings instantly became a defining moment for America, for college students, and for the anti-war movement. The Crosby, Stills, and Nash song "Ohio" (with its angry refrain: "Four dead in Ohio") was on the radio within weeks of the event. Within days of the killings, there was the first and (to date) only nationwide student strike, which shut down over 400 campuses across America. Also within days, over 100,000 people demonstrated in Washington, D.C., which (bizarrely) prompted President Richard Nixon to drive out to the Lincoln Memorial at four o'clock in the morning to have a rambling debate with some of the protesters -- one of the strangest interactions between any president and any protest group in American history, I would venture to guess.

So much has been written about the actual Kent State shootings, though (James Michener has a pretty good non-fiction book on the subject, if you're interested in reading about the event in detail), that I would like to point out two things which generally don't get remembered as being tied to the event itself, one of which was a cause of the incident, and one a result.

The first is why the Kent State students were demonstrating in the first place. Because it wasn't just some run-of-the-mill anti-war rally or protest taking place on the streets of Kent forty years ago. It was part of a nationwide reaction to an announcement President Nixon had made (on April 30), that the United States had essentially invaded Cambodia. Nixon thought if he pushed into Cambodia, it would deny the North Vietnamese military forces their "safe haven" there, from which they launched cross-border attacks into southern Vietnam. But the public saw it differently, as an expansion of an already-unpopular war effort into a whole new country. And Nixon's television address absolutely enraged the anti-war college students.

It's hard to draw parallels with today's world, but picture President Bush announcing in about 2006 or 2007 that American ground troops were pushing into Pakistan. Or perhaps Iran. Think of what America's reaction would have been. But this doesn't even really come close, for the simple fact that there is no military draft today. College-age kids don't have to worry that they will be shipped off to America's wars, since our military is today all-volunteer. This was not so in 1970. Your birthdate dictated whether you would be required to join the military, or whether you had lucked out in the lottery and didn't have to worry. The prospect of being forced to take part in a war certainly focuses your attention on the war's progress and strategies.

Now, I'm not going to get into "whose fault" the Kent State shootings were, here. You could argue they were Nixon's fault. You could argue they were at least partly the fault of the students' violence, although it's a stretch to make this punishment fit the perceived crime. I leave others to make arguments of this type from either perspective. The shootings happened at the end of four days of rage, which included trashing parts of downtown Kent and lighting bonfires in street intersections, and the torching of the R.O.T.C. building on campus. The Ohio National Guard had bayoneted students prior to the fourth of May, almost at random, according to students. Rocks were thrown at the Guardsmen, and tear gas was fired into the protest crowd. Neither side thought the demonstration that day was going to be a picnic.

The biggest culprit was likely an oversight on the part of whoever was deploying Ohio National Guard units -- the fact that they had been issued live ammunition in the first place. The unit which was sent to Kent was previously involved in an ongoing Teamsters dispute which was taking place all over Ohio at the time. And the Teamsters had been known to fire back at Guardsmen. So the unit was issued live ammo, in case it was needed. After the rioting in Kent (the day after Nixon's announcement), this Guard unit was transferred to Kent, and no one thought to collect the ammunition they had been given. Which is why they had live bullets in their guns to begin with.

This is not to apologize for the shootings in any way, I hasten to point out. Nothing can diminish the fact that National Guardsmen fired over sixty shots into a crowd of unarmed protesters, killing four people (two of whom were just walking from class to lunch, and hadn't even taken part in the protest), and wounding nine others.

But the second point I would like to make is that there was at least one thing which came out of the Kent State shootings which can be seen in a positive light. This was the development of better "non-lethal" crowd control methods. The problem with trying to police an unruly crowd (or riot) is that bullets don't do you much good, because they are quite literally "overkill." It's like atom bombs -- they're supposed to be useful in the threat, not in the actual deployment. Actually using them is so disproportionate to the situation that it's really not any sort of answer.

Up to the Kent State killings, the preferred "non-lethal" crowd control was tear gas. Real CS tear gas (not "pepper spray") is truly noxious stuff which causes vomiting and blinding pain in the eyes, and can be very effective in disbursing a crowd. If the wind is blowing the right direction, that is. The Guardsmen tried using tear gas in Kent, but the wind wasn't cooperating, and the students began throwing canisters back at the Guardsmen themselves.

The students weren't close enough to the Guardsmen for any actual physical hand-to-hand type of confrontation, and the Guard didn't really know the campus that well, leading them to (at one point) essentially "cornering" themselves against a fence. Even bayonets aren't much use at a range of more than seven or eight feet.

So, as a result of the Kent State tragedy (and a very similar shooting at Jackson State University ten days later), some thought was put into less lethal crowd control by the U.S. Army (and others). Eventually this led to the development of rubber bullets and "beanbag" bullets which could be used with much less severe results than live ammunition. Police departments and armed forces around the world today use these tools, which I choose to think of as Kent State's legacy.

I hope I'm not giving the impression that I'm on "one side" or "the other" of any particular demonstration or police force by doing so. Even rubber bullets, with enough determination (when used at point-blank range, in other words) can kill people. And getting shot, even at a distance, by a rubber bullet is not a pleasant experience, I'm told. I'm not making any excuses for the police in any given situation, in other words.

But I do think the ongoing development of such non-lethal crowd control measures is a relatively good thing, on a conceptual basis. Today, there are even some science-fiction methods (using sound waves or microwaves) being developed which have not yet been widely used, and which may have unforeseen problems. But the fact that the military is researching how to quell riots short of wholesale slaughter is indeed a good thing. Because putting some kids in uniform (most of the Guardsmen were roughly the same age as the protesters in Kent) and giving them a gun with live ammo isn't always the best way to break up a crowd. When the crowd you're trying to intimidate simply doesn't believe you'll use your gun, then having a gun as a threat becomes meaningless. But actually using your gun is not the answer either, because demonstrating against our government is not a capital offense in America, and should never be.

I am not, by nature, a big fan of the Pentagon. I think America is going to have to rein in our obscene military budget if we ever want to get our national budget back in the black. We are number one in the world in military spending, by far. We spend seven hundred and fifty billion dollars per year -- roughly ten times what the country who is number two on this list (China) spends per year. I think we cannot sustain this for very much longer, especially seeing as how China is the one lending us the money to do so.

My sympathies are also with the Kent State dead and wounded students, and not with the Guardsmen who shot them down, and never paid a legal price for having done so. Nixon's escalation and incursion into Cambodia was doubling down on a very bad bet, and ultimately did not work.

But, having said all of that, I am glad that one result of the Kent State killings was to give some thought as to how to avoid such situations in the future. While I sincerely hope I'm never shot by a rubber bullet, or experience a "heat ray" microwave crowd-disperser, I am actually thankful that research continues into more subtle forms of crowd control than live bullets, because I think lives have been saved by the fact that these methods now exist. As I said, it's hard to be positive about weapons development, but when it is less-than-deadly weapons development I do think it can be seen in a positive light.

Memorial to Jeffrey Miller, where he fell.

And that is what I choose to think of as at least one positive outcome of the Kent State tragedy. The next time you see police or the military trying to take on a riot -- by not firing live rounds into the crowd -- I invite you to think of it as the legacy of Jeffrey Miller, Allison Krause, William Schroeder, and Sandra Scheuer.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant