Late last week, Israeli Prime Minister Benjamin Netanyahu’s war against Iran became official. Israel launched a series of airstrikes targeting Iran’s nuclear facilities, government buildings and military headquarters, as well as military leaders and scientists. I write that the conflict “became official,” because for the past 20 months, Israel was already engaged in a proxy war against militant groups supported by Iran, whether Hamas in Gaza, Hezbollah in Lebanon or the Houthis in Yemen. Israel and Iran had also exchanged missile, drone and air strikes twice last year, in their first direct confrontation ever. And prior to that, they had been engaged in what many observers called a shadow war dating back a decade.

Now, as the head-on Israel-Iran War enters its second week, there are questions about how long the conflict will last and whether it will or won’t draw in other powers, namely the United States. But another key question pertains to understanding how the war started.

Israel initially claimed it launched the attacks to keep Iran from producing nuclear weapons, which it said Tehran was on the verge of doing. Iran has long maintained that its nuclear program is for strictly civilian purposes and denied it has any intention of weaponizing it. The consensus among Western intelligence agencies is that Tehran did pursue a nuclear weapon in the early 2000s, but subsequently abandoned those aims.

But in 2108, the U.S. under then-President withdrew from the multilateral nuclear deal known as the Joint Comprehensive Plan of Action, or JCPOA, which had placed rigorous constraints on Iran’s program, including strict oversight by the International Atomic Energy Agency. In response, Tehran ended its compliance with the deal, increasing its stockpiles of enriched uranium, raising the level to which it is enriched and refusing access to IAEA inspectors. As a result, there is no longer as much certainty or consensus about the state of Iran’s program or its intentions. Tehran still maintains it is for peaceful purposes. But notably, the day after Israel launched its first attacks, French President Emmanuel Macron said that Iran was nearing a “critical stage,” without further elaborating what that meant.

In any event, the Israeli strikes were not limited to Iran’s nuclear facilities, suggesting that the true goal of the war is regime change, with the understanding being that the only safe way to fully remove the threat of a nuclear-armed Iran is to remove the regime of the Islamic Republic. This same logic of regime change underpinned another war aimed at toppling the government of a “rogue state” that was also purportedly seeking to acquire nuclear weapons: the ill-advised U.S. invasion of Iraq in 2003.

In taking military action to stop, or at least slow, Iran’s nuclear program, Israel’s actions are being framed as defensive, by itself and at least some others. For instance, a recent joint statement by the leaders of Germany, the United Kingdom and France as well as the European Union’s foreign policy chief declared that Israel had a “right to protect its security and people, in adherence with international law.”

It might seem a matter of semantics, even academic navel-gazing, to wonder if Israel’s strikes against Iran should be labeled anticipatory, preemptive or preventive. But the distinction matters.

That the right to self-defense is a pillar of international law is without question. It is codified in Article 51 of the United Nations Charter. But is anticipatory self-defense actually self-defense? Using military means to destroy a nuclear program before being able to ascertain whether a hostile power has decided to build a bomb, let alone deploy or use one, pushes the limits of what can be plausibly defined as self-defense.

Some are using the more restrictive category of preemptive strike to describe Israel’s campaign, while others are calling it a preventive attack. In both cases, the idea is that the threat was real and it was better to fire the first shot now than to wait for Iran to arm itself with a bomb. Netanyahu argued as much after the fact, asserting in a public address to Israeli citizens that “the Iranian regime was planning to give the nuclear weapons that they would develop to their terrorist proxies.” Even if the threat was not immediately manifest, Netanyahu claimed that Israel’s leaders could not afford to “leave these threats for the next generation,” because if they “don’t act now, there will not be another generation.”

While both preemption and prevention follow a “better now than later” logic, they are not synonymous. Preemption refers to the use of force driven by evidence and fear of an imminent attack, for instance launching a strike against an adversary that is amassing troops on the border in preparation of an invasion. Prevention also refers to the use of force to stop a future attack by the opponent, but one that is not imminent or even actively planned. Instead, it is to forestall a permanent shift in the balance of power that could leave the attacking side at a disadvantage and even vulnerable to defeat in a future war. These are ultimately wars of choice, but with the perception that there really is no choice at all, with the result that all options for forestalling the negative shift remain on the table.

It might seem a matter of semantics, even academic navel-gazing, to wonder if the strikes should be labeled anticipatory, preemptive or preventive. But the distinction matters for how publics and the international community more widely perceive Israel’s attacks and the question of whether Israel merits assistance. It also matters for determining if Israel’s actions are legal under international law, which permits preemptive strikes, but not preventive ones. If not, they are yet another blow to the rules of the rules-based order that the U.N. Charter embodies, as if the bounds of self-defense are stretched too far, then any attack can become an act of self-defense.

One could argue, as did the historian AJP Taylor in his study of war between great powers, that every war begins as a preventive war, in that the side that struck first was seeking to forestall a less favorable outcome and felt that it had no choice but to act. Of course, whether that side truly thought it had no choice, or even whether it was truly trying to prevent a bad outcome, is always questionable. The sides may well have wanted war anyway. Given Netanyahu’s long history of seeing Iran as a threat that needed to be not only deterred, but fully defeated, it seems that the logic of prevention simply provided a convenient excuse to take an action aimed at settling the score once and for all.

There are reasons to question whether Iran, if it ever develops a bomb, would use it to threaten its neighbors, as opposed to deter the kind of attack Israel just launched. But what is clear is that Israel is not the only state in the region to see Iran as a threat. A primary purpose of the Abraham Accords initiative introduced by Trump during his first term and further pursued by former President Joe Biden is to bring together Arab nations that not only want to normalize relations with Israel, but share a common perception of Iran as an enemy. While Saudi Arabia, a key regional state not yet party to those accords, had recently pursued a diplomatic thaw with Iran, it too had been engaged in a long security and diplomatic rivalry with Tehran, one that had already escalated into proxy conflict in Yemen.

This suggests that had Israel not struck Iran now, it or another state in the region might have at some point in the near future. Indeed, it is arguably this very hostility that drove Iran to adopt the ambiguous posture it has with its nuclear program. Fundamentally, Iran perceives the region as inhospitable, and its neighbors, including Israel, see Iran as inhospitable to the region. Such conditions create a security dilemma that makes trigger fingers itchy and the logic of “better now than later” attractive. Something was going to give, and it finally did.