ASPI's Peter Jennings yesterday drew parallels between President Obama's recent West Point speech and a 1950 speech by then US Secretary of State Dean Acheson which set geographic boundaries to US interests in Asia. South Korea was placed outside those boundaries, and the speech is widely thought to have encouraged Pyongyang and Moscow to believe that they could invade South Korea without US retaliation.

According to Jennings, Obama's speech, in which the President said the US would only use force to protect 'core interests', has sent the same message to America's contemporary adversaries:

Around the world, America’s frenemies now know that they have a free hand to push the limits of their own aggressive intensions against neighbours. All they have to do is avoid harming American ‘core interests’, itself a flexible concept. Obama’s West Point speech repeats in all fundamental respects the same disastrous errors of Dean Acheson’s 1950 oration. Emphasising what America will not do in international affairs only emboldens the world’s zealots, nationalists and chauvinists to fill the vacuum created by absent US power.

Peter might have drawn on other examples to illustrate what America will not do in international affairs. For instance, the US opposed the Soviet incorporation of the Baltic republics in 1944, but took no military action to stop it. Nor did it send tanks into Hungary in 1956 to resist the Soviet invasion, or into Prague in 1968. Then there was China's war against Vietnam in 1979, various wars and skirmishes between India and Pakistan since partition, and countless civil and international conflicts in Africa and South America.

You get the point: American foreign policy is, like that of every country, defined by limits, of both resources and interests.

In fact, that sentiment is so obvious it borders on trite. So why should Obama not articulate it? What is controversial about a US president saying that there are a whole bunch of conflicts the US will not get involved in? Surely it would be much more extraordinary if a US president were to declare that his country's foreign policy had no limits? But of course, we've been there:

So it is the policy of the United States to seek and support the growth of democratic movements and institutions in every nation and culture, with the ultimate goal of ending tyranny in our world.

That's from George W Bush's second inaugural, delivered in January 2005, though even that sweeping statement was immediately followed by the caveat that 'This is not primarily the task of arms'. Unfortunately, Bush was about two years late to this realisation. A more sober assessment of the limits of American power in early 2003 might have  saved Bush from making the greatest strategic blunder of any president since the Vietnam War.

Peter Jennings thinks that, in articulating the limits of American power, Obama has emboldened groups such as ISIS in their take-over of Iraq. He says 'Small crises...have a way of growing into bigger ones, and sooner or later those will infringe core interests. The message for Barack Obama should be if you aren’t prepared to fight small fires, you’d better get ready to fight bigger ones.' That sounds like a call for the US to be permanently prepared to pre-emptively intervene in essentially any local conflict anywhere, a sentiment more at home in the heady early months of the Afghanistan invasion or Operation Iraqi Freedom. Our experience since then should have taught us that even 'small fires' are often beyond the ability of the US to put out. In fact, trying to put them out is what got Iraq into this mess in the first place.

It's not the articulation of limits that has weakened America over the last decade or more, but the refusal to accept any limits. Obama's speech was a necessary correction to that over-reach.