By Jeremy Bowen
BBC Middle East Editor
It is not yet war between Israel and Lebanon, but these are acts of war.
Israel has made a highly escalated response
Israel has described what happened on Wednesday, when two Israeli soldiers were captured, eight killed and two injured in a Hezbollah ambush, as an act of war.
It has retaliated with highly escalated acts of war, which are calculated to put a great deal of pressure on the civilian population.
As in Gaza - where an Israeli soldier is being held by Palestinian militant groups, including the military wing of Hamas - it is not just trying to get its people back, it is trying to deliver severe blows to Hamas and Hezbollah - trying to change the rules of the game.
The leader of Hezbollah, Sheikh Hasan Nasrallah, has said that his men acted to support the Palestinians - and that he was prepared to negotiate a prisoner exchange with Israel, which has been done before.
But Israeli Prime Minister Ehud Olmert rejected that as emphatically as he ruled out negotiations with Hamas when they suggested the same thing.
It is difficult to see an easy way out.
The pressure on Mr Olmert, an inexperienced leader in his first big crisis, has increased exponentially.
Hezbollah has proved itself a formidable enemy.
In Gaza, Palestinians are likely to face more, not less, Israeli military pressure.
Will the Americans intervene diplomatically? Perhaps, if it gets too bad.
But Israel's calculation appears to be that, in the post-11 September 2001 world, with the US very tied up in Iraq, it has time on its side.
What has happened around the border between Israel and Lebanon is intimately connected with what has been happening in Gaza.
This crisis shows, yet again, how the conflict between the Palestinians and the Israelis is able to destabilise their neighbours.
Lebanon is dealing with an Israeli land invasion for the first time since 2000, when Israel ended a 22-year occupation of the south. It will be expecting punitive raids on its infrastructure closer to Beirut.
Syria had already been threatened by Israel because of its links with Hamas. It has much stronger links with Hezbollah.
The risks now, for the region, are considerable.