JERUSALEM — Cracks are emerging in Israel’s military.

The Middle East’s best equipped and most powerful force is under one of the worst assaults it has encountered — a battle within its own ranks.

A contentious government plan to overhaul the country’s judiciary has cleaved deep rifts within Israeli society. Those rifts have infiltrated the military, where reservists in key units have pledged not to show up for duty if the legislative changes are pushed through.

The letters, signed by thousands of reservists over the last seven months, have up to now mostly remained threats. But this week, 161 critical air force personnel announced they will stop their service, raising concerns about the military’s readiness in the face of similar refusals at a time of heightened violence and tensions on several fronts. On Wednesday, hundreds of reservists from various units joined a rally in Tel Aviv, declaring they would not report for duty anymore.

Why Are Reservists Refusing to Show Up?

Israel’s military is compulsory for most Jewish men. After their three-year service is complete, many continue reserve duty well into their 40s or beyond.

Reservists make up a critical pool of soldiers who fill an important role in reinforcing the regular army. They cover a range of positions and forces, from air to land to sea to cyber.

As soon as Prime Minister Benjamin Netanyahu’s government announced the overhaul in January, reservist-led protest groups become central to the grassroots movement demonstrating against the overhaul.

The protesters say they do not want to serve a country that they think is moving toward dictatorship if the overhaul moves ahead. They say the government is violating an unwritten social contract where soldiers risk their lives with the understanding that they are defending a democracy.

Many also believe that loosening judicial oversight could expose Israeli forces to war crimes charges at international courts. One of Israel’s defenses against war crimes accusations is that it has an independent legal system capable of investigating any potential wrongdoing.

How Is the Military Being Affected?

The refusals have largely remained threats, having no immediate impact on the army’s readiness. But the declaration from the 161 air force personnel “immediately” halting their service has sent a shock through the establishment.

Israel relies on its air force to strike enemy targets in neighboring Syria. It also is an essential element of battles against militants in the Hamas-ruled Gaza Strip, operations that have become more frequent in recent years. Unmanned aircraft have recently also been used in the West Bank. Israel also has threatened to prevent Iran from developing a nuclear weapon — and a strike on Iran would almost certainly would require warplanes.

All of those fronts require Israel to maintain a highly trained roster of pilots who can be called at little notice to stage airstrikes. When a pilot refuses to show up for training for even just a couple of weeks, his readiness is affected. When ground personnel like those who signed this week’s letter, which include target identifiers or coordination experts, refuse to show up, the entire system is shaken.

“I need to maintain competency,” said Maj. S., one of the letter’s signatories, in an interview with Israeli Army Radio, saying that if he doesn’t stay abreast of system updates and operational plans, he can’t do his job. “There is no doubt that this harms the country.” He was not identified in line with military rules.

What Is Being Done to Halt the Refusals?

Fears about the potential effect of refusals to serve on the military’s readiness pushed the country’s defense minister, Yoav Gallant, to publicly criticize the overhaul in March. That prompted Netanyahu to fire him, setting off a burst of spontaneous protests and a labor strike that forced the Israeli leader to freeze the overhaul and reinstate Gallant.

But this time around, Gallant is silent and political leaders appear to be taking a harder line.

“Refusal to serve endangers the security of every citizen of Israel. The government will not accept refusal to serve,” Netanyahu told his Cabinet this week, promising unspecified action against the protest.

The military’s top brass have been caught in a balancing act over showing empathy to the concerns of their troops, protecting cohesion within the military despite the deepening societal divisions over the overhaul and ensuring the political dispute doesn’t affect the military’s performance.

But, in what appears to be a response to growing pressure from political ranks, military leaders have stiffened their tone against those who refuse.

Israel’s military chief, Lt. Gen. Herzi Halevi, visited an air base on Wednesday and met with his air force chief and other top commanders.

He urged for “the cohesion” of active and reserve forces, and called the reservists “an inseparable part” of the military. But, he warned that that “calls for not showing up to reserve service harm the military.”