President Trump’s plan to place Gaza under American occupation and transfer its two million Palestinian residents has delighted the Israeli right, horrified Palestinians, shocked America’s Arab allies and confounded regional analysts who saw it as unworkable.

For some experts, the idea felt so unlikely — would Mr. Trump really risk American troops in another intractable battle against militant Islamists in the Middle East? — that they wondered if it was simply the opening bid in a new round of negotiations over Gaza’s future.

To the Israeli right, Mr. Trump’s plan unraveled decades of unwelcome orthodoxy on the Israeli-Palestinian conflict, raising the possibility of negating the militant threat in Gaza without the need to create a Palestinian state. In particular, settler leaders hailed it as a route by which they might ultimately resettle Gaza with Jewish civilians — a long-held desire.

To Palestinians, the proposal would constitute ethnic cleansing on a more terrifying scale than any displacement they have experienced since 1948, when roughly 800,000 Arabs were expelled or forced to flee during the wars surrounding the creation of the Jewish state.

“Outrageous,” said Prof. Mkhaimar Abusada, a Palestinian political analyst from Gaza who was displaced from his home during the war. “Palestinians would rather live in tents next to their destroyed homes rather than relocate to another place.”

“Very important,” wrote Itamar Ben-Gvir, a far-right Israeli lawmaker and settler leader, in a social media post. “The only solution to Gaza is to encourage the migration of Gazans.”