Fox News chief foreign correspondent Trey Yingst provides key takeaways from his conversation with Ukrainian President Zelenskyy after Putin lowered Russia's threshold for nuclear arms.

No, the ATACMS strike is not the start of World War III. Ukraine’s forces hit six military targets inside Russia, behind the Russian lines where Ukraine is fighting over the border near Kursk.

The Army Tactical Missile System (ATACMS) has been used by Ukraine before, but this strike came after the Biden White House granted new permissions to hit on Russian soil.

President Biden has done President-elect Trump a favor with this U-turn decision on ATACMs. Striking Russian ammunition and troop concentrations feeding the battle against Ukraine applies pressure on Russia and makes a lot of sense. As secretary of state nominee Sen. Marco Rubio has said, Ukraine needs leverage. ATACMS helps.

Ukrainian President Volodymyr Zelenskyy and President-elect Trump (Kay Nietfeld/picture alliance | Curtis Means/Daily Mail/Bloomberg)

"Those missiles clear a grid square, a square kilometer," then-Maj. Gen. David Petraeus said of ATACMS in 2003, when he was commanding the 101st Airborne Division on the march up to Baghdad. The U.S. Army V Corps ended up firing 414 ATACMs during Operation Iraqi Freedom, often packaged with Apache helicopters.

1,000 DAYS OF WAR IN UKRAINE AS ZELENSKYY DOUBLES DOWN ON AERIAL OPTIONS........

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