Lee Smith over at the Weekly Standard has written an excellent introduction to Iran’s efforts to supply Palestinian extremists with guns. It’s a roundabout route—by sea from Iran to Sudan, then by land through Egypt and the Sinai, then down the tunnels into Gaza. Iranian personnel are believed to be present for at least some of this process; the Israelis periodically attack.

A new, non-Iranian source has also emerged: Libya. Gaddafi’s vast stocks of weapons were a boon to the international black market in small arms; the Standard shows a photo of a masked terrorist holding a Belgian assault rifle (a photo drolly cited “courtesy of Hamas”). This highlights two of the key challenges of modern global security: first, how do you arm your allies (or any state, if your arms industry is to be treated as just another business) without adding to insecurity in the long run? As the New York Times’ C. J. Chivers once illustrated, weapons last a long time—sometimes longer than the governments that control them. Second, how do you respond to state breakdowns that threaten international security? With its small stock of chemical weapons, large stock of conventional weapons, and proximity to Europe, the collapsing Libya was a danger to its neighborhood. Yet the world’s response did little to address that, and the new Libya is hardly a state in the Westphalian sense; Smith’s article highlights the problems such shell-states can cause.

So why is the Islamic Republic arming Hamas? The most straightforward reason is that it limits Israel’s regional strength. During the November campaign against Hamas, Operation Pillar of Cloud, nobody was talking about bombing Iran. Israel was consumed with its immediate security. Long-range Iranian rockets amplified Hamas’ power, and forced the Israelis to devote energy to hunting them down. There’s a deterrent element here—Tehran wants the Israelis to worry that an operation against the nuclear program will lead not only to retaliation from Iran, but also to a rain of rockets from Gaza in the southwest and Hezbollah in the north. Israel would then be fighting on several fronts at once and potentially facing more internal dissent.

But there’s another, deeper reason for Iran’s arms shipments. A key part of Iran’s brand at home and abroad is being the most powerful advocate of “resistance”—rejection of Israel and of the West’s regional role. Resistance is a key raison d’être of the Islamic Revolution, and the Palestinian conflict is by far the hottest issue for supporters of resistance. Hence Iran has aligned itself with Palestinian hardliners and eagerly trumpeted its ties to them when they act. Every rocket that lands in Israel and every Palestinian casualty strengthens the resistance narrative that accommodating Israel has accomplished nothing, and that struggle is the only way. The analogy to Iran's troubled relations with the West is obvious. The dark secret behind the guns for Hamas and other extremists, then, is Iran has no interest in an Israeli-Palestinian peace. It wants the conflict—and the suffering of the Palestinian civilians it claims to support—to be endless.