Still fighting Israel’s outside enemies on multiple fronts, Prime Minister Benjamin Netanyahu woke up on Monday to a new political battlefield at home.

The departure this weekend of Benny Gantz and his centrist National Unity party from Israel’s emergency wartime government is unlikely to immediately sever Mr. Netanyahu’s grip on power. The prime minister’s governing coalition still commands a narrow majority of 64 seats in the 120-seat Parliament.

But Mr. Gantz’s move means that Mr. Netanyahu is now totally dependent on his far right and ultra-Orthodox coalition partners as he prosecutes the war in Gaza in the face of mounting international opprobrium, leaving him increasingly isolated and exposed at home and abroad.

Mr. Gantz and Gadi Eisenkot, another powerful member of National Unity, also left Mr. Netanyahu’s small war cabinet. They are both former military chiefs who were widely viewed as key voices of moderation in the five-member body, which was formed in October after the Hamas-led assault on Israel prompted the Israeli bombardment and ground invasion of Gaza.

The two centrist politicians raised public confidence in the government’s decision-making process at a time of national trauma. They also lent the war cabinet an aura of legitimacy and consensus as Israel fought Hamas in Gaza, as well as its archenemy Iran and its other proxies, including the powerful Hezbollah militia across Israel’s northern border with Lebanon.

Mr. Gantz accused Mr. Netanyahu of “political procrastination,” suggesting that he had been putting off critical strategic decisions to ensure his political survival. His decision to quit the wartime government ushers in a new period of political instability and left many Israelis wondering where the country goes from here.