A Chinese leader going to Japan is a rare occurrence. The visit by Hu Jintao to Tokyo is only the second time since 1945 that Japan has hosted the leader of the world's most populous country.
The first, a decade ago by Jiang Zemin, was widely viewed as a diplomatic disaster with Jiang demanding the Japanese "learn from history'' a coded criticism of Tokyo's refusal to apologise for wartime atrocities.
So this visit can, justifiably, be described by that overused word, landmark. It has the potential to be a turning point in Sino-Japanese ties after years of hostility. There is much at stake.
China has now overtaken the US as Japan's main export market and it desperately needs Japanese investment and technological expertise. Beijing and Tokyo realise that the emergence of India will have a direct impact on their economic outlook.
While both countries have reached out to the sub-continent they also understand that as Asian neighbours they will gain far more financially if the thorny question of history can be put to one side.
This trip is about business and officials have hinted that both sides have agreed to avoid discussing controversial issues such as Japan's wartime record, China's conduct on human rights, Taiwan, and Tokyo's bid for a permanent seat on the UN Security Council.
These are all important subjects which at some point will have to be tackled - but not just yet.
Greater co-operation between Tokyo and Beijing is still a novel concept and is far from certain. The history of these two countries provides too many opportunities for accusation rather than agreement, for mistrust rather than confidence.
But for the first time in recent history there is a feeling that both China and Japan could work closely together. If so, it will shape our century.
