Australia, a less important ally, drew the appropriate conclusion. From that time on, Australia has never deviated significantly from the American position on any major issue. Indeed, apart from occasional rhetorical and pain-relieving complaints from members of Labour governments, it has cleaved scrupulously to that position. Thus did one Australian prime minister pledge to go “All The Way With LBJ”, while another promised a possibly bemused Richard Nixon that Australia would “Go a-Waltzing Matilda With You.” To be fair, Australian governments have usually acted out of conviction as well as expediency. But the interests and beliefs of politicians are rarely allowed to collide, and an awareness of the advantages of the alliance—they include favorable access to technology and intelligence, as well as the all-important security insurance policy—has certainly helped shape those convictions.

It is against this background that Australia’s reaction to the events of September 11, 2001 is best understood. As it happens, Australia’s Prime Minister, John Howard, was in Washington, D.C. on that very day. Undoubtedly, he was as shocked and horrified as anyone else who witnessed those events at first hand. But the nature of his immediate response represented more than shock and sympathy. It was entirely in accord with Australia’s mindset and behavior over previous decades.

“Australia”, Howard announced on September 12, “will provide all the support that might be requested of us by the United States in relation to any action that might be taken.” This astonishingly unqualified commitment—note the words “all” and “any”—was made at a time when the nature of the American response, and the demands on Australia it might involve, were completely unknown.

Despite the sweeping nature of Howard’s promise, and despite the radical direction that U.S. policy was to take, the Australian government has honored that commitment to an exceptional degree. Indeed, it has virtually marched in foreign policy lockstep with Washington over...