By Paul Reynolds
BBC News Online world affairs correspondent
The dust has settled a bit after Mr Sharon's visit to Washington and it is clear that his plan has produced one of those Middle East moments when everything has changed.
Sharon plan is backed by President Bush
It does not mean that the conflict will not continue. It obviously will. But the terms of the conflict have been altered.
The so-called roadmap to peace, the plan drawn up by the quartet of the UN, the US, the EU and Russia, had already been exposed as unrealistic. It has now in reality been rolled up.
Claims by President George W Bush and the UK Prime Minister Tony Blair that somehow the roadmap is being implemented by the Sharon plan cannot be taken too literally.
What they mean is that negotiations can and should continue.
But it will be on a new basis.
The Palestinians will have to accept as facts two principles which they wanted to be the subject of negotiations.
One is the permanence of major Israeli settlements on the West Bank.
The other is that Palestinian refugees from earlier wars will not be allowed back into what is now Israel.
This is a major blow for the Palestinians, as Mr Sharon, in candid remarks before he left for Washington, said it was designed to be.
He even suggested that it could preclude a Palestinian state.
It is possible that he could be wrong on that, but certainly if the Palestinians eventually choose to talk on the new basis, their state will be a small and fragmented place.
What Palestinians could gain
The US and UK will argue that the Palestinians have gained something.
They will get an Israeli withdrawal from Gaza and the major Israeli settlements named as permanent do not include many others whose future is presumably for negotiation.
They will also argue that many small and fragmented states have done rather well.
Many Palestinians, however, might not choose to talk but to fight.
Other defining moments
The Sharon plan and the Bush backing for it stand comparison with other moments when great powers have helped shape the politics of the Israeli/Palestinian conflict.
In 1917, the then superpower Great Britain, through the Declaration named after the Foreign Secretary Lord Balfour, promised a "national home for the Jewish people in Palestine".
The Balfour Declaration, bitterly recalled to any British visitor to any Palestinian refugee camp, set the scene for large scale Jewish immigration and settlement while supposedly safeguarding the "civil and religious rights of the non- Jewish communities".
This dual aim proved impossible to sustain and in 1939, Britain reshaped the terms again with a White Paper which severely restricted Jewish immigration for five years and then gave Palestinians a veto on any more, thereby aiming to prevent the emergence of a State of Israel.
This plan, too, eventually collapsed and Britain withdrew.
Then the Israelis started creating further facts on the ground.
Mr Sharon played his own significant role in creating those facts, in peace and in war.
He has sometime been successful. His crossing of the Suez Canal in the 1973 war with Egypt, which threatened the encirclement of the Egyptian army, is already a classic text in the history books.
But not always. His invasion of Lebanon in 1982, designed to end Palestinian resistance, is also a classic for different reasons. It failed.
It is not possible to say whether his latest plan will work or not. And of course what works for one side does not necessarily work for the other.
But it has created new political facts which will have to be taken into account.
Mr Sharon is doing as a politician what he did as a soldier. He is trying to define the battlefield.
It is also possible, probable even, that nothing will happen diplomatically and that Israel will withdraw into a Biblical type "stronghold" of the type favoured by the Old Testament warrior Gideon, whose exploits provided the inspiration for the modern Israeli military.
The barrier now being put up by the Israeli government between Israelis and Palestinians is perhaps evidence that this is already happening.