For more than a decade, Israel has tried to hem in Hamas, the militant Palestinian group that controls the Gaza Strip.

It has blockaded the Islamist militia into the tiny Mediterranean enclave, fought three wars with it and, in a delicate dance with Egypt and Qatar, figured out a way to placate it — allowing the Qataris to pay public sector salaries, letting Palestinian fishermen venture out to the Mediterranean Sea and permitting a few extra hours of electricity a day into the impoverished territory.

There was an unspoken policy in Israel “that quiet would be answered with quiet”, said Shaul Shay, the former deputy head of Israel’s National Security Council and an intelligence officer in the military’s southern command. But with Israel and Hamas engulfed in the most serious conflict since 2014, “we are now eating the fruits of this process”, he said. As of Thursday morning, 83 people have been killed in Gaza and seven in Israel, including one soldier.

Inside the Israeli military, concerns had been building that Hamas had spent the years since its last war in 2014 building up a critical mass of rockets, mortars and other weapons. Hamas has “quite a vast arsenal of rockets”, said Israel Defense Forces Lt Col Jonathan Conricus. Militants in Gaza have stockpiles of between 20,000 and 30,000 rockets and mortars today, mostly homemade, “on a par with the fire capability of small European countries and their rockets can strike almost all densely populated areas of Israel”.

“They have quite a nice cottage industry and they produce rockets based on blueprints and advice that they have gotten from Iran and others,” he added.

On Tuesday night, Hamas — considered a terrorist group by the US, the EU and Israel — showed exactly how well-stocked its arsenal was. In volley after volley designed to defeat Israel’s multibillion-dollar Iron Dome interceptor missiles, it fired at least 1,000 rockets and has continued to fire hundreds more.

In Tel Aviv and Beer Sheva, some 60 kilometres south of Gaza, air raid sirens sent Israelis running to bomb shelters. The Israeli parliament was briefly cleared, and the Jewish state’s only international airport in Tel Aviv was closed.

Chart showing Hamas & OIJ missile launches into Israel on May 10th 2021 compared to 2019/20 (updated May 13 2021)

Many of them are crude projectiles but they made their mark on the Israeli psyche. “I know they’re not dangerous, but still, you’re terrified,” said Alizza, a teacher in Tel Aviv, who spent hours huddled in her apartment’s safe room with her two children.

Israel has vowed a broad campaign to bring Hamas to heel, carried out hundreds of air strikes, killed 14 Hamas militants, including senior commanders in the Qassam Brigade, an elite military unit, and pounded the entire strip to root out rocket launch sites.

The conflagration started on Monday, when Hamas waded into a weeks-long stand-off between Palestinian youth at al-Aqsa mosque in Jerusalem and Israeli police over restrictions around the site and planned evictions to make way for Jewish settlers.

As the protests snowballed and hundreds of Palestinians were wounded by police, Hamas saw an opportunity, said Ahmed Yousef, who has advised Ismail Haniyeh, the charismatic political head of the Islamist group. It set a 6pm deadline for Israeli police to leave the mosque and for settlers to quit the Sheikh Jarrah neighbourhood from where Israel has long planned to evict Palestinians. Israel’s annexation of East Jerusalem since the 1967 war has not been recognised by the international community.

“They waited for the Israelis to say that enough is enough, that it will stop its own Jewish rightwing extremists, and when they didn’t, Hamas decided to send a warning,” said Yousef, speaking from Istanbul, where Turkish President Recep Tayyip Erdogan has welcomed the group. “They calculate everything — they know what the cost is, and they are willing to pay the price.”

A minute after 6pm, seven rockets streaked through Israeli airspace, with air raid sirens drowning out the celebrations of Jewish ultranationalists marking the anniversary of Israel’s 1967 capture of Jerusalem. With this week’s attacks, the Islamist group has displayed its ability to strike deep into Israeli territory and has also manoeuvred itself back into the position of the most muscular champion of Palestinian rights, eclipsing its political rival Fatah.

Speaking from Qatar, Ismail Haniyeh was already claiming a victory. “We have managed to create an equation linking the Jerusalem and Gaza fronts,” he said in a speech that was played on a loop on Arab news channels.

The Israeli military had not anticipated the “decision by Hamas to fire at Jerusalem and continue to fire relentlessly at Israeli communities”, said Israel’s Conricus. “We thought we had communicated clearly what the consequences would be.”

For Hamas, despite the loss of life and damage to Gaza, there was little to lose, said Mkhaimar Abusada, a professor of political science at Al-Azhar University in Gaza. “To lose a few buildings here and there, to lose a training camp, that’s not costly for Hamas, ” he said.

But now Hamas, with its home-made rockets, meagrely armed soldiers and cash-starved military is facing off against Israel’s air force, the most powerful in the Middle East, and risking the prospect of a ground invasion.

And Hamas’ rocket arsenal, while vast, is mostly crude. “The rockets definitely terrorise, but are they capable of causing significant military damage? Not quite,” said Conricus, pointing out that Israel’s Iron Dome defence system was intercepting 90 per cent of them.

Diagram showing the Hamas arsenal

Despite military superiority, a clear victory has eluded the Israelis in past conflicts with Hamas. The last war in 2014, dragged on for 67 days, and more than 2,000 Palestinians and 73 Israelis, mostly soldiers, were killed. In the end, Hamas declared itself victorious, while Israel felt it had done enough damage to the group’s military wing to buy itself a few years of peace.

Shay said the only way for Israel to contain the threat was to change its strategy towards Hamas and more proactively target the militant group’s military facilities — even during times of relative calm.

“As long as the formula remains the same, it’s more or less the same scenario . . . and it’s working in the favour of Hamas.”