The signal came in two parts: As Mr. Pence reiterated America’s commitment to Israeli-Palestinian peace, every member of the governing right-wing coalition stayed silent while opposition legislators rose to applaud. More stunningly, the Knesset’s speaker, Yuli Edelstein, declared that Israel will “develop the whole of the country, including Judea and Samaria,” referring to the biblical names for the entire West Bank.

But none of the legislative initiatives toward that goal addresses the implications for Israel’s security that would come with them. That is a potentially fatal lapse, because what now seems to be under serious consideration would have disastrous consequences for Israel’s security and would undermine American interests throughout the Middle East.

It is no accident that none of the proposals suggests annexing the entire West Bank. Even the most zealous legislators realize that absorbing all of the West Bank’s 2.7 million Palestinians would threaten Israel’s existence as a Jewish and democratic state.

Consequently, those seeking to block prospects for separation from the Palestinians into two states look for a “luxurious annexation”: absorb as much of the land, with as little of the population, as possible.

Competing proposals put forward by the end of January included annexing all Jewish settlements in the West Bank without touching areas populated by Palestinians. Another would annex the Gush Etzion and Ariel settlement blocs plus the Jordan Valley. Yet another would create a region called “Greater Jerusalem.”

The most popular among annexationists was perhaps the most extreme: Education Minister Naftali Bennett’s proposal calling for the annexation of “only” the 60 percent of West Bank land designated Area C (Israel’s major settlement blocs now occupy about 7 percent of Area C). The area surrounds 169 “islands” of Palestinian towns (called Area A) and villages (Area B). Spread throughout Area C and in isolation from one another, these disconnected 169 communities, which constitute the remaining 40 percent of West Bank land, would not be annexed.

That’s the plan. But how would it work? What would be the fate of the 300,000 Palestinians now living in Area C? Logic dictates that Israel would have to offer them citizenship or a permanent residence status equal to that of Palestinian residents of East Jerusalem. Either status would have to bring free movement throughout Israel.

Even though movement from the West Bank is restricted by a security barrier, a few terrorists even now manage to enter Israel. With Area C annexed, identifying the few bad guys seeking to kill Israelis among the 300,000 new Palestinian Israelis from Area C (who would have unfettered access to Israel) would be difficult and costly.

The physical barriers required to prevent residents of Areas A and B from filtering into Area C en route to Israel would be a security nightmare. The perimeter of each of the 169 Palestinian islands would have to be treated as an international border. To separate the annexed land from the islands they encircle, 1,200 miles of new barriers would be required, along with hundreds of security gates that would allow controlled Palestinian movement from one enclave to another or from their enclaves to land of theirs in Area C (where 75 percent of the land is owned by Palestinians). The cost of building such a barrier system would be about $10 billion, and constructing the gates, along with associated security measures, would cost far more.

Palestinians would view Israeli annexation as a game-changer, foreclosing the option of a viable Palestinian state. The Palestinian Authority would collapse, and Israel would have to impose martial law and provide basic services to all Palestinians in the West Bank. Defense Minister Avigdor Lieberman has estimated the annual cost of social security alone for Palestinians at $6 billion. The yearly cost of health, education and other government services could be $5 billion more.

With the collapse of the Palestinian Authority, Palestinian-Israeli security coordination would vanish. Many of the Palestinian troops would turn their weapons on Israelis, and the Palestinian street would most likely explode. This would leave Israel’s military and its domestic security agency, Shin Bet, to take full security responsibility not just in the newly annexed Area C, but also for the millions of Palestinians in Areas A and B, where Palestinian security agencies now operate in close coordination with the Israel Defense Forces.

This, in turn, would necessitate an increase in the I.D.F.’s presence throughout the West Bank; the standing army could not do the job alone and a mobilization of reserves would be required. This, too, would tax the Israeli economy and severely diminish military preparedness for other security threats, most directly from Syria, where Iran seeks to establish a presence, and Lebanon, where Hezbollah has become more experienced at combat.

Arab governments might not be able to ignore potentially violent domestic expressions of outrage at Israel’s actions. Accordingly, Israel’s diplomatic and security relationships with Egypt and Jordan might not survive, and chances for additional relationships would vanish.

Israel’s relationship with the American Jewish community would also be jeopardized, with annexation attempts further alienating large numbers of American Jews and accelerating the alarming trend of Jewish youth distancing themselves from Israel — a trend that undermines a major pillar of Israel’s long-term national security.

And not only Israel would suffer. All of this would come back to haunt the Trump administration, by undermining its efforts to forge an American-led regional coalition harnessing the resources of Israel and moderate Arab states to check Iran’s hegemonic ambitions — a goal that serves the strategic interests of all.

We are both former Israeli generals, but we are not alone in these comments. They are based on the findings of a task force composed of members of a network of over 275 retired generals from all of Israel’s security services, who retain the view that an eventual two-state solution is essential to Israel’s security, as well as to its Jewish and democratic character.

A two-state solution may not soon be in the cards. But preserving conditions for an eventual separation from the Palestinians must remain a primary Israeli strategic objective. No annexation fantasy can be allowed to undercut it.
It is the height of irresponsibility for Israeli politicians to propose annexation and for Americans, if they care at all about Israel, to egg them on.

Danny Yatom, a retired major general who was the director of the Mossad intelligence agency, is a member of the steering committee of Commanders for Israel’s Security. Amnon Reshef, a retired major general who was commanding general of Israel’s Armored Corps, is the chairman of the network.