President Biden has agreed to send another Patriot missile battery to Ukraine, coming at a time when the country is struggling to defend against Russian attacks. The Patriot missile battery is one of the best air-defense weapons, but the U.S. and its allies only possess a limited supply. This new Patriot system will come from Poland, and could be deployed to Ukraine’s front lines within the next few days. The system contains a powerful radar system as well as mobile launchers which fire missiles towards incoming projectiles. However, it is also one of the scarcest weapons systems that the U.S. possesses, and demand for them has been high with conflict in the Middle East and rising tensions on the Korean Peninsula. The Patriot is also by far the most expensive single weapon system that the U.S. has supplied Ukraine with, costing about $1.1 billion.