EmbedshareWider Europe Briefing: What's NATO new Eastern Sentry? Eight countries have already joined Eastern Sentry and placed assets at the disposal of NATO's supreme allied commander (SACEUR) Alexus Grynkewich. First, the lack of any new American assets being provided to Eastern Sentry so far. Eastern Sentry is thus a sort of sudden measure until apotential "drone wall"can become a reality and complement what is already out there. As Grynkewich put it when pressed by the media after unveiling Eastern Sentry: "It's time to take a fresh look at this.