Anniversaries of events that shook the world are a test of how much they still shape our affairs. In that respect, the 10th anniversary today of the September 11 attacks on the US stands out. Some argue the attacks did not change the world so much as serve as a wake-up call about a growing global security threat. But to most of us, the words in this newspaper's editorial the day after the attacks remain pertinent - the vulnerability of the world's mightiest nation made us aware how vulnerable we all are.
There is no question that this peacetime horror that beggared belief still shapes the world's affairs. The decade since 9/11 has been momentous. The attack thawed chilly Sino-US relations as China condemned terrorism and Washington changed its diplomatic priorities. The US remains engaged in two wars that have added trillions of dollars to the post-financial-crisis national debt, which has polarised domestic politics as never before, redefined relations with China - its largest creditor - and weighed on Hong Kong with its currency peg to the US dollar.
The cold-blooded and carefully calculated attack on people who were simply going about their everyday lives left almost 3,000 dead. Many more have died in terror attacks around the world since then. There was a need for the international community to respond and at first the US received much sympathy and support. Sadly, that goodwill was squandered by the US and its allies amid the mistreatment of suspects, the rewriting of the rules of combat and other breaches of human rights committed in the name of the war on terror.
Having driven the al-Qaeda-friendly Taleban from Afghanistan with international blessing, Washington severely strained strategic relationships with the ill-conceived invasion of Iraq, which also weakened the focus on stabilising Afghanistan. Those relationships did not begin to improve again until the election of Barack Obama.
It took a decade to track down Osama bin Laden. He may be dead and al-Qaeda diminished, but things will never be the same. It is impossible to predict, for example, when ever-more sophisticated and invasive surveillance measures will no longer add to travel time and costs, or when events like the Olympic Games or international conferences no longer involve massive security operations.
Obama and Chief Executive Donald Tsang Yam-kuen have both reflected on events 10 years ago and expressed hopes for peace and tolerance in articles published by this newspaper today. Our thoughts are with those who lost loved ones in the attacks or have otherwise suffered as a result of them. The harrowing images of September 11, 2001, will always serve as a reminder of the need for nations to work together and strive for a safer, more peaceful world.