JERUSALEM (Reuters) - Benjamin Netanyahu was one of the most polarising leaders in Israel's history long before the International Criminal Court prosecutor's office said on Monday it had requested an arrest warrant against him over possible war crimes in Gaza.

But in the volatile world of Israeli politics, the announcement drew a wave of solidarity with the prime minister, whose political future has looked more uncertain as the war in Gaza has dragged on into its eighth month.

Netanyahu is an unmatched political operator, at home in both the bare knuckle world of Israeli politics and the international diplomatic arena, where his flawless American English has been a trademark for decades.

But the man once known as "King Bibi" to his supporters faces an increasingly hostile climate.

Netanyahu's hawkish image was badly tarnished by the attack by Hamas gunmen on Oct. 7, with most Israelis blaming him for the security failures that allowed the deadliest assault since the founding of the state more than 75 years ago.

An open split over the conduct of the war has erupted between the prime minister and a clutch of former generals including his own defence minister, who have demanded he explain his strategic goals for the war. As he struggles to hold together his wartime coalition, Netanyahu has been looking more and more isolated.

The scale of the Oct. 7 killings, accounts of brutality and images of violence in the southern Israeli communities around Gaza, where some 1,200 Israelis and foreigners were killed and around 250 taken hostage, caused profound trauma in Israel.

At the same time, the shattered terrain in Gaza, where more than 35,000 people have been killed in Israel's assault, have put the country under greater international pressure than it has faced in decades, including from its most steadfast ally the United States.

The world court prosecutor's office is looking into accusations of criminal responsibility for war crimes and crimes against humanity both during the devastating Hamas attack on Israel and during Israel's relentless military response.

For the moment at least, the announcement by the ICC's prosecutor has been enough to rally Israelis, including his main potential challenger and even the opposition, to defend the prime minister against what President Isaac Herzog described as a "one-sided move" taken in bad faith.

Netanyahu himself described the announcement as "absurd" and said it was directed against the whole of Israel, an example of the "new antisemitism" he said had moved from college campuses to the justice system.

As well as Netanyahu and Defence Minister Yoav Gallant, the prosecutor is looking at action against three Hamas leaders, including Yahya Sinwar, the Islamist movement's leader in Gaza and one of the main architects of the Oct. 7 attack.

The parallel between democratically elected leaders and the heads of a movement banned as a terrorist organization in many Western countries has caused the most outrage in Israel and won Netanyahu at least a momentary taste of domestic solidarity.

LONGEST SERVING PRIME MINISTER

A former member of an elite special forces unit that carried out some of Israel's most daring hostage rescues, Netanyahu has dominated Israeli politics for decades, becoming Israel's longest-serving prime minister when he won an unprecedented sixth term in 2022.

His alliance with hard-right national religious parties was key to his victory and he faced some of the biggest protests in Israel's history last year over a package of measures designed to curb the powers of the Supreme Court that drew accusations he was undermining the foundations of the country's democracy.

But bitterly fought as the judicial overhaul was, his record is likely to be overshadowed by the disaster of Oct. 7 and the subsequent Israeli campaign in Gaza, which led to the ICC prosecutor's move.

The 74-year-old, whose popularity had been further damaged by a trial on corruption charges that he denies, has refused to accept personal responsibility for Oct. 7. He has said only that everyone will have to answer difficult questions when the war with Hamas is over and has dismissed calls to resign and hold early elections.

Although U.S. President Joe Biden described the ICC announcement as "outrageous", it has added one more international obstacle for Israel to negotiate.

The war in Gaza has drawn a renewed focus on the expansion of Israeli settlements in the occupied West Bank and fuelled increasing calls for a revival of the peace process with Palestinians, which he has long opposed and which his hard right allies view as an anathema.

At the same time, Netanyahu's prized goal of a normalization deal with Saudi Arabia, building on the Abraham Accords with Gulf States achieved in his previous term, appears to have run into the sands.

If an arrest warrant comes, reaching that deal and getting his foreign policy back on track will become even more complicated.

(Writing by Angus McDowall and James Mackenzie; Editing by Cynthia Osterman)

By James Mackenzie