(Mosaic) John Spencer and Solomon Moshkevich - At the start of this war, the jihadist group had governing authority, territorial control, a functioning bureaucracy, and a trained army. On October 7, 2023, Hamas fighters from Gaza launched one of the most brutal assaults on Israeli soil since the country's founding -- killing civilians, seizing hostages, and briefly occupying territory. The attack was quickly labeled a "terror attack," and Hamas, a U.S.-designated Foreign Terrorist Organization, was cast once again in the role of a group of religious extremists operating outside of the system of sovereign states. This framing, though familiar, is flawed. It creates misperceptions about the scale, nature, and legal classification of the conflict Israel now faces. And it misleads both policymakers and the public about the rules that govern this conflict, the expectations of response, and the real meaning of proportionality. It is time to stop calling Hamas just a "terrorist organization." This argument is, of course, heard most often from those who would claim that Hamas consists of "freedom fighters" and that the term terrorist is unfairly biased or even a sign of racial prejudice. The case we make here is very different, and not moralistic, but legal and strategic. Undoubtedly, Hamas is a terrorist organization that has committed countless acts that fit any standard definition of the term. But in addition it is a political-military entity with governing authority, territorial control, and a functioning bureaucracy. It maintains a trained army, organizes military campaigns, and conducts operations that resemble traditional armed conflict far more than they resemble isolated acts of terrorism. Labeling Hamas a terrorist group undermines the legal clarity and strategic understanding necessary to fight and win a war. It also distorts public perception of what Israel is actually doing and what it is allowed to do under the law of armed conflict. The attack of October 7 was not an isolated act of terror; it was a cross-border, combined-arms military operation, that is, an invasion. This invasion involved thousands of trained fighters who breached Israel's air, land, and sea defenses; killed civilians and soldiers alike; and seized territory, while operatives in the rear simultaneously fired rockets deep into Israeli territory. Hamas attempted to coordinate its assault with Hizbullah to open a northern front. Like any conventional military invasion, the attack posed an immediate, existential risk to the state of Israel, and the IDF has since admitted that its Gaza Division was initially overrun and defeated by the enemy. This was an act of war. Hamas may use terrorist tactics, but it is an armed force fighting in a war. The semantics matter. They always have. But in war, they can mean the difference between legitimacy and condemnation, between clarity and chaos, between victory and defeat.