Article 5 of NATO’s treaty states that an armed attack on one member is an attack on all. But it cannot be invoked by one member state alone, requiring NATO consensus. It is also not necessarily a requirement that NATO members respond militarily. Article 5 was invoked for the first time after the September 11 terrorist attacks on the United States in 2001. Eight measures were enacted to support the United States, including intelligence sharing, providing aerial radar patrols over the US, and naval patrols in the Mediterranean. With the latest missile that killed two in Poland, even if it had come from Russia, William Alberque, director of strategy, technology and arms control for International Institute for Strategic Studies, said that it probably would fall short of what is intended by Article 5. “‘Deliberate armed attack’ is a real thing. Two misfired cruise or ballistic missiles ain’t it.”