The reported U.S. plan to provide Ukraine with the Patriot air defense system will impede Moscow's strategy of pressuring Kyiv into negotiations by destroying the country's critical infrastructure. But outstanding questions regarding the delivery of the system and Ukraine's needs for other military hardware mean it will also not give a decisive edge to Ukraine. On Dec. 13, U.S. media reported that Washington was preparing to provide the Patriot surface-to-air missile system to Ukraine. Patriot systems could reportedly arrive in the war-torn country in a matter of weeks once Ukrainian troops finish training to use them in an accelerated program at a U.S. military base in Germany. The Patriot has different models of varying capabilities, but can have up to eight launchers that can each hold four missiles with the capacity to strike targets as far away as 99 miles (approximately 160 kilometers), depending on the model. On Dec. 15,...