Terrorism is an emotive term that has often been used to demonise one's political opponents. This has occurred on both so-called "sides" in the "War on Terrorism" that Bush pushed into his rhetoric. This overzealous, polarising use of the term has lead to wide international disagreements and the result is that really, one can't use the term without implying a lot more than the base original meaning. This makes it inappropriate for use in international discussions and it should - in my opinion - be dropped out of professional terminology entirely and replaced with other jargon.
Back to the base meaning. Terrorism can literally be described as violent action used to spread fear. There have historically been very few military actions that haven't in result had ramifications of widespread fear. With that said, the intent to cause fear isn't necessarily there on a wider scale in the force engaging in action. It can be an unintended result. But you'd be irresponsible to expect anything different. If you send gunners or drop bombs into a place full of civilians, the natural human response to such danger is to panic. Therefore, as Michael Franti sometimes puts it, "all bombing [read: all war] is terrorism". The problem with saying that, of course, is that calling it terrorism makes the more simple among us immediately think that it means "war=bad". It's actually a direct statement of fact, stating the easy logic that war causes terror, therefore conducting warfare is terrorism. But it's so difficult for many of us to separate the fact of the term from the emotions we attach to it.
While one man's terrorist could be another man's freedom fighter, I personally think that both have little right to take life. The only people who can allowably take life have to be able to bring it back, thereby making death and suffering reversible things, and so far that's impossible and a mere fantasy. War will realistically continue, but so will its injustice.
Of course, I'd never want to force my opinions on this to anyone else. I just think peace, and not forced peace but the peace of free will, must be sought, and that means that I disagree with pre-emptive warfare and the "other" mentality we place upon our fellow humans by calling them terrorists or any other emotionally laden word. Even people who kill others are humans, no matter how hard that is to accept, and therefore we should ideally be less ready than most nations are to take their lives for some "greater good". Only then can humanity come to grips with its' insane power to do good or evil, and turn its' back on the latter.
With the realities settled in and the injustice to a large extent unavoidable into the near future, there is obviously a need for a military force to defend each nation. If a nation is under a direct - and I don't mean this "oh some nation we don't like might have/be getting nuclear weaponry" idea, but literally "I have the weapon and now I'm going to blow up your country" kind of threat, then military action is justified in that the lives saved will ultimately outnumber the lives ended by conflict, and that an actual threat exists rather than what could be an invented one. So the existence of a military and its functions for a state as a Defense rather than a more appropriately named Attack Force (which would be a better name for some Western defense forces in terms of the conduct their politics has at times forced on them) makes sense.
Some people have pointed out so-called similarities between environmental movements and terrorist movements. I think that's a comparison of which most of you should be ashamed. Terrorist movements use military action to destroy lives. Environmental movements reduce pollution with the aspiration to save human life as well as other life, which we need to survive. Never the twain shall meet, except in one or two tiny extremist movements which are, like terrorist movements, implied to be the heads of the larger movement when in fact they're a tiny portion which is heavily divided from the rest.
And while some of you used Greenpeace as an example, I must point out that though they may break a few laws, they don't kill people. Newsflash of the year: that would go against, you know, "peace". Their main ideal.
