Goods into and out of Gaza are strictly monitored by Israeli and Egyptian authorities, neither of whom are friends with Hamas.

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Homemade Qassam rockets now compliment an increasingly sophisticated arsenal of weapons

But despite that, over 1,200 rockets have still made their way over the border of the coastal enclave towards Israel in recent weeks. Worryingly, the IDF estimates there to be thousands more.

Israeli military figures know who is firing these rockets (Islamic Jihad and militants from the armed wing of Gaza’s ruling party, Hamas). They also know, roughly, how many are left (about 5,000 standard mortars, plus a few hundred longer-range rockets capable of hitting central and northern Israel).

But other aspects are lesser known. Who pays for them, for instance? Who builds them? Where and how are they assembled? And are we still talking about the crude Qassam (pictured), or are we seeing an increasingly sophisticated range?

Moreover, if there is a naval blockade and a supply-line squeeze that is virtually water-tight now that the Egyptians have closed the tunnels, where on earth are these weapons coming from?

Gaza-based journalist Nidal Al-Mughrabi, writing for Reuters, has analysed Gaza’s homemade rocket industry, and the results are enlightening.

First, we hear, the rockets are not arriving ready-made, but rather are being assembled in the Strip, and this makes IDF estimates unreliable.

“Hamas does not depend on imported weapons and is making its own so fighters may be engaged in combat and others make them the ammunition,” says Hamza Abu Shanab, an expert on Islamist groups in Gaza.

“Israel cannot guess the size of Hamas’s arsenal because the tools are being made locally. So for every rocket fired, another ten are made.”

Jane Intelligence, a British defence industry consultancy, said the new rockets and launchers that militants had made themselves “makes them less dependent on rockets smuggled into the Gaza Strip to threaten Israel’s main population centres”.

Israeli military figures point the finger at Iran for the supply of parts, but can’t say how those parts are now getting through, nor how Hamas has since got hold of more sophisticated weaponry, such as the armed drone shot down over Israel on Monday.

Alongside the long-range rockets capable of reaching Haifa, Hamas has this year also been able to boast the “Ababeel,” described as the group’s first bomb-carrying unmanned aerial craft.

All this is part and parcel of the war Hamas is waging against Israel, and the group’s commanders are pleased to make progress on that front.

“What you are seeing today is not metal and power, what you see today is blood,” one said recently. “Thousands of people paid with their lives so that we and our people can see the day Israeli leaders stood before their nation to say: ‘Sorry, Tel Aviv was hit’.”