Israeli Prime Minister Benjamin Netanyahu fired Defence Minister Yoav Gallant on Tuesday, citing a "crisis of trust", and replaced him with Israel Katz, previously the foreign minister.
The prime minister named Gideon Saar as the new foreign minister, Netanyahu's office said in a statement.
Gallant and Netanyahu, both in the right-wing Likud party, have clashed for months over the objectives of Israel's 13-month-old war in Gaza against Palestinian militant group Hamas.
Netanyahu said Gallant has made statements that "contradict the decisions of the government and the decisions of the cabinet". In response, Gallant said: "The security of the state of Israel always was and will always remain my life’s mission."
Katz said on social media platform X that he would approach his new role "with a sense of mission and holy fear for the security of the State of Israel and its citizens."
Reports appeared in September that Netanyahu, under pressure from far-right coalition partners, was considering firing Gallant.
Protests erupted in Tel Aviv and other parts of Israel after Gallant's firing.
"Firing Gallant in the middle of a war is an act of madness," said Israeli opposition leader Yair Lapid on X.
In Washington, a spokesperson for the White House National Security Council said Gallant had been an important partner and that it would continue working collaboratively with Katz.
"America's commitment to Israel's security remains ironclad and the U.S. Department of Defense will continue to work closely with Israel’s next Minister of Defense," Pentagon spokesman Major General Patrick Ryder said in a statement.
By Steven Scheer and Nidal al-Mughrabi