President Donald Trump, Ukrainian President Volodymyr Zelensky, and various European leaders are focused on “security guarantees” to uphold any possible peace settlement between Russia and Ukraine.

Ideas on the table range from the deployment of European troops in Ukraine to collective defense guarantees along the lines of NATO’s Article 5, which commits all NATO members to recognize an attack on one member as an attack on all members, thus requiring a mutual defense response. The logic here is that unless Ukraine’s security is entrenched by force of defensive arms, any pause in the fighting will simply set the stage for another Russian assault five, 10, or 15 years down the road.