Israel was taken by surprise by the most ambitious operation Hamas has ever launched from Gaza.

The scale of what’s been happening is unprecedented. Hamas breached the wire that separates Gaza from Israel in multiple places in the most serious cross-border attack Israel has faced in more than a generation.

It came a day after the 50th anniversary of the surprise attack by Egypt and Syria in 1973 that started a major Middle East war. The significance of the date will not have been lost on the Hamas leadership.

Israel’s Prime Minister Benjamin Netanyahu says his country is at war and will exact a heavy price from its enemies.

Videos and photos of dead Israelis, civilians as well as soldiers, are all over social media.

Other videos of armed men from Hamas hauling soldiers and civilians into captivity in Gaza have enraged and alarmed Israelis.

Within hours Israel was responding with air strikes into Gaza, killing many Palestinians. Its generals will be planning a ground operation next.

The presence of Israeli hostages there means it will be even more complicated than previous incursions.

For months, it has been clear that there was a deepening risk of an explosion between Palestinian armed groups and Israel. How and where it happened was a total surprise, outside the armed wing of Hamas.

Israelis and Palestinians have been focusing on the West Bank, the territory between Jerusalem and the Jordanian border that Israel has occupied since 1967, where there has been almost continuous confrontation and violence throughout the year.

Armed Palestinians, especially those operating out of the West Bank towns of Jenin and Nablus, have attacked Israeli soldiers and Jewish settlers.

The Israeli army has mounted dozens of raids. Armed settlers have taken the law into their own hands, with reprisals against Palestinian villages.

Extreme religious nationalists inside Israel’s right-wing government have repeated their claim that the occupied territories, in their entirety, are Jewish land.

No one expected Hamas to conceive and meticulously plan such a complex and coordinated operation out of Gaza.

Recriminations have already started in Israel about the failure of its intelligence services to see what was coming. Israelis expect that an extensive network of informers, agents and high-tech surveillance will do its job.

In the end, Israeli intelligence was blindsided by the Hamas operation, which came when Israelis were relaxing or praying during the weekend of a religious holiday.

Hamas has said it acted because of threats to Jerusalem’s mosques. During the last week, some Jews have prayed inside the Aqsa Mosque compound, the third holiest place for Muslims after Mecca and Medina in Saudi Arabia.

The same precinct is also venerated by Jews, as it was the site of the biblical Jewish temple. Prayer by religious Jews on what they call the Temple Mount might not sound like much, but it is prohibited by Israel as Palestinians consider it highly provocative.

Even so, by the standards of Jerusalem, always a tinderbox of national and religious conflict, it was not exceptionally tense.

The complexity of the Hamas operation shows that it had been planned over months. It was not a hasty response to events in Jerusalem in the last week or so.

The reasons why Hamas and Israel are once again at war run much deeper. The conflict between Israelis and Palestinians has been heating up even when it is far from the headlines of international news organisations.

Even so, it has been largely ignored by countries that still officially call for peace via a two-state solution, shorthand for an independent Palestine alongside Israel. For a while, during the Oslo peace process of the 1990s, the prospect of two states was a real hope. Now it is an empty slogan.

The Palestinian-Israeli conflict has not been a priority for President Joe Biden’s administration in Washington DC. It has been trying to find a way to offer security guarantees to Saudi Arabia in return for a rapprochement with Israel.

The last American attempt to relaunch a peace process failed a decade ago, during the administration of President Barack Obama.

At the heart of the trouble is the intractable and unresolved century-long conflict between Arabs and Jews for control of the land between the Mediterranean Sea and the river Jordan. These rapidly-escalating events prove once again that the conflict cannot simply be managed. When it is left to fester, violence and bloodshed are guaranteed.