In south Asia, there is no wall to tear down, as there was in Berlin. Yet the quarrel between two of the regions' great powers has lasted longer than the Cold War, and blown intermittently hot. Since independence from the British, India and Pakistan have persisted in sniping - and occasionally firing - at each other, each blaming the other, mutually suspicious, unable to reconcile despite their long shared history. Yet, as an American official pointed out this week, the two countries face a looming threat, one which seeks to pit them against each other - and one which they can only defeat together.
Speaking this week in New Delhi, Robert Gates, the US secretary of defence, warned that al Qa'eda and similarly inspired groups would seek to destabilise not only Afghanistan and Pakistan, but also India. The fear is that further attacks, such as the 2008 Mumbai attacks, might push the two nuclear-armed nations to war. For extremist groups, he said, are interconnected and "a victory for one was a victory for all".
Gates has made such warnings before, signalling that the US now considers that to be a chief strategy of al Qa'eda and extremist groups inspired by them. Indeed, it is in the interests of these groups to foment chaos, for it is in the spaces between the intentions of states, and in the geographical areas inaccessible to them, that such organisations thrive. Gates made his warning before jumping on a plane for an unannounced two-day visit to Pakistan, his first since Barack Obama took office. While there, he elaborated on the theme in an article for a Pakistani English-language newspaper, emphasising the common threat extremists posed to Pakistan and the US, and writing of the "tremendous sacrifice of so many Pakistani troops" in the line of duty.
One of the reasons for Gates's appearance in Rawalpindi is that the US wants to bring Pakistan into a wider global role, recognising its stability is vital for the region. In addition to its long borders with Afghanistan and India, Pakistan also shares borders with China and Iran, both countries around which America needs to tread carefully. It is easy for the watching world to see how instability in one part of Asia will have repercussions in others, and to also see that the solution lies in co-operation between nations. But the politics of the region are fiendishly complex. It is not too optimistic to believe that this looming threat might be the glue that finally binds India and Pakistan together - but it is not too pessimistic to believe both sides will probably let the opportunity slip. For the wounds of suspicion are deep. As easy as it is to say that political differences should be set aside, in India and Pakistan, mistrust runs deep and goes back far, even to Partition.
There are many on both sides who are in no mood to forgive. The two have fought three wars since gaining independence and lost millions of their citizens in the upheaval of Partition, when the two states were formed and refugees fled their homes for the safety of their co-religionists. Yet the religious division of the countries is not complete - Pakistan has millions of Hindus and India millions of Muslims - and the familial metaphors are correct, because the two share a long history: indeed, under the British Raj, they were one entity.
Much has soured ties since those days, not least the failure to find a clear settlement to the Kashmir question, Pakistan's accusations of Indian involvement in Baluchistan, its restive western province, and the machinations of both sides in the long proxy battles in Afghanistan. But it was the audacious attacks in Mumbai in 2008 that have truly poisoned relations. India has since refused to resume peace talks until the Pakistanis crack down on militants blamed for carrying out the attacks. The suspicion has long lingered in New Delhi, and elsewhere, that Islamabad is either too soft on terrorists operating from its territory, or actively tolerating them.
And as with brothers, even perceived slights become wounds. Just this week a new row broke out when no Pakistani players were chosen by Indian teams to play in an Indian cricket league, although players from other countries were chosen and Pakistani players have in the past featured prominently in the league. What is, in essence, a sporting dispute took on the nature of a diplomatic incident, with India's External Affairs ministry wading into the row and the Pakistani government canceling a delegation to India. That is how fraught relations are.
Yet a peace dividend is clearly in the interests of both countries, and despite the past, the two countries face a common future - and a common threat. As the Mumbai attacks showed, the hydra of terrorism, while coated in local language and grievances, does not respect national boundaries and what happens in Pakistan has repercussions across south Asia. India is mistaken if it thinks what happens in Pakistan can stay in Pakistan - the 2008 attacks have shown how global this battle is, and if Pakistan goes down, it may well take India with it.
This is what the US secretary of defense meant when he said: "It's dangerous to single out any one of these groups and say, 'If we could beat that group that would solve the problem,' because they are in effect a syndicate of terrorist operators." The problems in "Af-Pak" are not confined to any one country and are likely to spill over into others. India and Pakistan would do better to recognise their future lies together, not at the expense of the other. Together they comprise 20 per cent of the world's population, men and women who are overwhelmingly young and eager for a prosperous future - a future that will be more difficult to achieve the longer this cold war continues.
Despite differences, India and Pakistan share a great cultural heritage and their twin aspirations for global power status can be achieved more readily in tandem than in competition. For India, there is an understandable tendency to want to stand back from the fray. It is proud of its growing economic might and, while it has involved itself in rebuilding Afghanistan, it is wary of being seen to tread in Pakistan's sphere of influence: suspicion in Pakistan over its role in Afghanistan runs high.
Yet Islamabad would do well to reach out to its neighbour, given the significant threats that besiege it. And New Delhi would do well to reciprocate, openly and transparently, sensitive to its own and Pakistan's public opinion. All of these are fine judgments and the logistics of peace are never easy. But the price of war is higher and this relatively cold war has gone on too long. To encourage a thaw may require Pakistan and India to bear arms once more, not against each other, but against a common enemy. In the hot war against terrorism may lie the seeds of peace.
Faisal al Yafai was named Journalist of the Year at the 2009 Muslim Writers Awards. He is a Churchill Fellow for 2009/10.