As the Syrian civil war spills across borders, the capacity of battle-hardened extremist groups to come after us only increases. Regional aggression that goes unchecked, whether in southern Ukraine or the South China Sea or anywhere else in the world, will ultimately impact our allies, and could draw in our military. We can’t ignore what happens beyond our boundaries.

And beyond these narrow rationales, I believe we have a real stake -- abiding self-interest -- in making sure our children and our grandchildren grow up in a world where schoolgirls are not kidnapped; where individuals aren’t slaughtered because of tribe or faith or political belief.

I believe that a world of greater freedom and tolerance is not only a moral imperative; it also helps keep us safe.

But to say that we have an interest in pursuing peace and freedom beyond our borders is not to say that every problem has a military solution. Since World War II, some of our most costly mistakes came not from our restraint but from our willingness to rush into military adventures without thinking through the consequences, without building international support and legitimacy for our action, without leveling with the American people about the sacrifices required. Tough talk often draws headlines, but war rarely conforms to slogans. As General Eisenhower, someone with hard-earned knowledge on this subject, said at this ceremony in 1947, “War is mankind’s most tragic and stupid folly; to seek or advise its deliberate provocation is a black crime against all men.”

Like Eisenhower, this generation of men and women in uniform know all too well the wages of war, and that includes those of you here at West Point. Four of the service members who stood in the audience when I announced the surge of our forces in Afghanistan gave their lives in that effort. A lot more were wounded.

I believe America’s security demanded those deployments. But I am haunted by those deaths. I am haunted by those wounds. And I would betray my duty to you, and to the country we love, if I sent you into harm’s way simply because I saw a problem somewhere in the world that needed to be fixed, or because I was worried about critics who think military intervention is the only way for America to avoid looking weak.

Here’s my bottom line: America must always lead on the world stage. If we don’t, no one else will. The military that you have joined is, and always will be, the backbone of that leadership. But U.S. military action cannot be the only -- or even primary -- component of our leadership in every instance. Just because we have the best hammer does not mean that every problem is a nail.

And because the costs associated with military action are so high, you should expect every civilian leader -- and especially your commander in chief -- to be clear about how that awesome power should be used. So let me spend the rest of my time describing my vision for how the United States of America, and our military, should lead in the years to come, for you will be part of that leadership.

First, let me repeat a principle I put forward at the outset of my presidency: The United States will use military force, unilaterally if necessary, when our core interests demand it -- when our people are threatened; when our livelihoods are at stake; when the security of our allies is in danger.

In these circumstances, we still need to ask tough questions about whether our actions are proportional and effective and just. International opinion matters, but America should never ask permission to protect our people, our homeland or our way of life. (Applause.)

On the other hand, when issues of global concern do not pose a direct threat to the United States, when such issues are at stake, when crises arise that stir our conscience or push the world in a more dangerous direction but do not directly threaten us, then the threshold for military action must be higher. In such circumstances, we should not go it alone. Instead, we must mobilize allies and partners to take collective action. We have to broaden our tools to include diplomacy and development, sanctions and isolation, appeals to international law, and, if just, necessary and effective, multilateral military action. In such circumstances, we have to work with others because collective action in these circumstances is more likely to succeed, more likely to be sustained, less likely to lead to costly mistakes.

This leads to my second point. For the foreseeable future, the most direct threat to America, at home and abroad, remains terrorism, but a strategy that involves invading every country that harbors terrorist networks is naive and unsustainable. I believe we must shift our counterterrorism strategy, drawing on the successes and shortcomings of our experience in Iraq and Afghanistan, to more effectively partner with countries where terrorist networks seek a foothold.

And the need for a new strategy reflects the fact that today’s principal threat no longer comes from a centralized al-Qaida leadership. Instead it comes from decentralized al-Qaida affiliates and extremists, many with agendas focused in the countries where they operate. And this lessens the possibility of large-scale 9/11-style attacks against the homeland, but it heightens the danger of U.S. personnel overseas being attacked, as we saw in Benghazi. It heightens the danger to less defensible targets, as we saw in a shopping mall in Nairobi. So we have to develop a strategy that matches this diffuse threat, one that expands our reach without sending forces that stretch our military too thin or stir up local resentments.

We need partners to fight terrorists alongside us. And empowering partners is a large part of what we have done and what we are currently doing in Afghanistan. Together with our allies, America struck huge blows against al-Qaida core and pushed back against an insurgency that threatened to overrun the country.

But sustaining this progress depends on the ability of Afghans to do the job. And that’s why we trained hundreds of thousands of Afghan soldiers and police. Earlier this spring, those forces -- those Afghan forces -- secured an election in which Afghans voted for the first democratic transfer of power in their history. And at the end of this year, a new Afghan president will be in office, and America’s combat mission will be over.

此外，跳出這些狹隘的理論框架來看，我認為大家還存在著一個真正的共同關切——持久的個人利益，那就是要始終確保我們的子孫后代成長在這樣一個世界當中，在那里，人們不會因為種族、信仰或政治理念的迥異而劫持女學生或濫殺無辜。

我認為，建設一個更加自由及包容的世界不僅在道德上勢在必行，而且有助于維護我們自身安全。

盡管我們有意向在全球倡導和平與自由，但這并不意味著我們要借助軍事手段來解決每個問題。二戰結束以來，我們所犯的那些嚴重的錯誤，皆源自我們傾向于以訴諸武力的方式來解決問題，而對后果考慮不周、缺乏國際支持及法律支持，也沒有向美國人民交代他們需要作出的犧牲，以使他們心中有數。雖然強硬的表態時常占據報紙頭條，但戰爭卻很少與口號“步調一致”。正如對這個問題深有體會的艾森豪威爾將軍（General Eisenhower），于1947年在西點軍校畢業典禮上所說的那樣：“戰爭是人類最悲慘、最愚笨的蠢行，無論是蓄意挑起戰爭，還是為其獻計獻策，這都是對全人類犯下的滔天罪行?！?/p>

與他一樣，這一代的軍人——無論男女，都對戰爭理解深刻。這其中也包括了你們西點畢業生。在我宣布增兵阿富汗時，聽眾當中的4名服役人員后來就在那里壯烈犧牲。此外，還有許多西點士兵受傷。

我認為，出于維護美國國家安全的考慮，這些軍事部署是很有必要的。但是，這些傷亡者的英魂和傷痛一直縈繞在我的腦海、令我難安。如果我將你們派上戰場，僅僅是因為世界某地出現問題需要處理，或是擔心批評家會將軍事不作為視作是美國軟弱的表現，那么，我就違背了自己對你們、對這個我們所愛國家的職責了。

我的底線是：美國必須在世界范圍保持領導力。如果我們不能，沒人能。你們所加入的美軍，永遠都是美國領導世界的中堅力量。但是美國的軍事行動不是我們展現領導力的唯一方式，更不是主要部分。因為雖然我們有最好的錘子(美軍)，但并不意味著每個問題都是釘子。

因為軍事行動代價極大，所以你們應該期望每個平民領袖——尤其是你們的總司令——清楚如何使用這一令人生畏的力量。所以，讓我用剩下的時間來描述一下我的想法：關于美國和美軍在未來幾年應怎樣領導世界，而你們將會成為領導世界力量的一部分。

首先，讓我重申一下我在就任總統時提出的原則：當我們的核心利益需要的時候——我們的人民受到威脅、生計受到威脅、盟友的安全處于危險之中——如果有必要，美國將單方面使用軍事力量。

當然在這些情況下，我們仍然需要捫心自問，我們的行動是否合適有效公正。雖然國際輿論很重要，但是在保護我們的人民、祖國和生活方式這些問題上，美國不需要得到別人的許可。(掌聲)

另一方面，當引起世界關注但沒有直接威脅到美國利益的危機產生時，當這些問題亟待解決時，當能觸動我們的良心或推動世界向更危險的方向發展但不對美國構成直接威脅的危機出現時，我們更不能輕易采取軍事行動。在這種情況下，我們不應該單打獨斗。相反，我們必須動員盟友和合作伙伴采取集體行動。我們應該廣泛使用各種手段，包括外交和發展、制裁和孤立、訴諸于國際法，甚至在必要情況下采取多邊軍事行動。在這些情況下，我們必須與其他國家合作，因為集體行動更容易成功，持續性強，還可以減少代價慘痛的錯誤。”

這引出了我的第二個觀點。在可預見的未來，不管國內還是國外，對美國最直接的威脅仍是恐怖主義。但是，那種對每個包庇恐怖主義組織的國家都采取進攻手段的戰略未免過于天真，也不可能長期進行。我認為，我們必須從伊拉克和阿富汗問題上汲取經驗和教訓，將美國打擊恐怖主義的戰略轉變為與那些國內有恐怖組織基地的國家進行有效的伙伴合作。

并且，對新戰略的需求反映出一個事實：今天我們主要的威脅不再是來自于基地組織的集中領導，而是來自分散的“基地”組織分支機構和極端分子，其中很多都在他們從事活動的國家內進行活動。雖然這種情況降低了美國本土遭受大規模9?11式襲擊的可能性，但是就像我們在班加西（Benghazi）看到的那樣，這會增加美國海外人員遇險的可能性。就像我們在內羅畢（Nairobi）購物商場看到的那樣，這還會增加防備薄弱目標遇險的可能性。因此，我們需要制定戰略應對這種傳播式的威脅，這一戰略必須能夠在不派遣軍隊、避免戰線過長、避免引發當地不滿情緒的前提下擴大我們的影響力。

我們需要合作伙伴一起打擊恐怖分子。我們在阿富汗已經完成和正在進行的工作，很大一部份是為了增進伙伴的自治能力。在與盟友的共同努力下，美國給基地組織核心造成了沉重的打擊，挫敗了其試圖顛覆國家的叛亂活動。

但是，決定這個進程能否持續下去的是阿富汗人民在處理這一問題上的能力。這就是我們訓練成千上萬的阿富汗士兵和警察的原因。今年春天早些時候，這些部隊，這些阿富汗部隊保障了選舉的進行，阿富汗人為該國史上第一次政權的民主移交進行了投票。今年年底，阿富汗新總統將上任，屆時美國作戰部隊的使命也將完成。（掌聲）