In a move likely to further deepen divisions among Israelis, Prime Minister Netanyahu Sunday fired his top security aide, defense minister Yoav Gallant, and will likely replace him with the current agricultural minister, Avi Dichter. 

The cabinet reshuffle came as soon as Mr. Netanyahu returned from a weekend trip to London, and a day after Mr. Gallant made public his opposition to a legislative drive to overhaul Israel’s judicial system. Mr. Netanyahu is determined to pass the legislation this week, before the Knesset goes on a recess. 

Mr. Dichter, a former head of Israel’s internal security service, Shin Bet, initially expressed support for Mr. Gallant. Yet, on Sunday he said he is “coordinated” with Mr. Netanyahu and justice minister Yariv Levin, who plan to force a Knesset vote this week on a major part of the judicial reform plan.

Mr. Netanyahu’s ruling coalition relies on 64 out of the Knesset’s 120 members for its majority. Mr. Gallant and three other members of the premier’s Likud party have indicated they would oppose the government in the upcoming vote. If they do so and bring with them just one other member of the coalition, Mr. Netanyahu’s vote would fail, dealing a major blow to the prime minister and jeopardize his hold on power. 

The judicial reform crisis has torn apart the country for more than12 weeks. Hundreds of thousands protesters have rallied against it on the streets. Army reservists, including Top Gun-type pilots, cyber warfare wizkids, and intelligence professionals, have made public their opposition to the legislation. Some of them failed to show up for training sessions to protest Mr. Netanyahu’s legislative effort.

Top security officials, reportedly including the army’s chief of staff, Lieutenant General Herzi Halevi, have warned Mr. Netanyahu that the legislation could threaten Israel’s ability to face crucial military challenges. Mr. Gallant made those concerns public Saturday night, leading to his firing Sunday.

“The security of the State of Israel is my life’s mission,” Mr. Gallant, a Likud stalwart and a former commander of the of Shayetet, an elite Israel Defense Force unit — the equivalent of the Navy SEALS — said in a dramatic televised speech Saturday. “The growing rift in our society is penetrating the IDF and security agencies. This poses a clear, immediate, and tangible threat to the security of the state. I will not allow this.”

He noted that he had long urged a major reform to relations between the legislature and the judicial branches. Yet, he added, “For the sake of Israel’s security, for the sake of our sons and daughters, the legislative process should be stopped.”

Mr. Gallant also called for an end to anti-government protests that have engulfed the country and for an end to any sign of refusal to serve by members of the Israeli military. With Iran nearing nuclear weapons capacity, Hezbollah arming up quickly, and growing Palestinian terror, he said, Israel cannot afford to be torn apart. 

Mr. Gallant originally planned to deliver his message on Thursday, but after a meeting with Mr. Netanyahu he decided to wait until the party leader addressed the nation. That day, Mr. Netanyahu called on the opposition to negotiate over the legislation but declined to announce a pause in the process.

Then, on Friday morning, Mr. Netanyahu flew to London for a meeting with Prime Minister Sunak.

In what could open a new front in the battle over the judiciary, Israel’s attorney general, Gali Baharav-Miara, said Friday that Mr. Netanyahu had reneged on a deal to stop meddling in the judiciary while corruption charges against him were playing out in the courts.

While some member of the ruling coalition criticized Mr. Gallant’s comments, others, including several senior Likud members, quickly expressed support for his call for dialogue. Those included a former Soviet refusenik Yuli Edelstein, former Jerusalem mayor Nir Barkat, and Mr. Dichter, who later vowed to vote in favor of the legislation.

On the other side of the ledger, party members led by the justice minister, Yariv Levin, and the Knesset judiciary committee head, Simcha Rothman, who have initiated the legislation drive, have threatened to resign if it were halted.