NATO's support for Ukraine has remained steadfast since Russia's invasion in 2022 and has frequently crossed its own red lines to provide military support.

But one area that has remained contentious is putting boots on the ground. That could change, with French President Emmanuel Macron suggesting that NATO troops could be deployed within Ukraine for training missions.

Russia condemned Macron's comments as "provocative," saying any foreign instructors would be "legitimate targets" for strikes. Whether or not Russia will act on its tough talk remains to be seen, but there is little doubt that NATO troops in Ukraine would constitute a significant escalation in the conflict.