Protected charging stations like a birds nest, autonomous pathfinding and a suit of sensors complemented by a good software suite for rotor drones complemented by fixed wing drones with massive optical arrays. And those legged dog drones. Border patrol can just work from home.
And a moat across the entire border.. with friggin sharks with friggin laser beams attached to their heads.
But seriously if my neighbor was Russia, I'd start building an anti tank moat, dragons teeth and the option for mines on either side of the moat. Use the potential minefield as farmland till it's needed as minefield. Pillboxes and a network of bunkers.