Russia's ongoing commitment of roughly 90 percent of its combat forces to the Ukraine conflict remains the dominant barrier to any near-term invasion of NATO territory, as Moscow continues rebuilding depleted conventional capabilities for potential limited operations on the eastern flank. A April 2026 assessment by the Netherlands Military Intelligence and Security Service indicated that Russia could assemble enough strength for a regional challenge to the alliance within a year after any Ukraine ceasefire, focused on testing Article 5 cohesion through small territorial gains rather than outright conquest. NATO has countered with reinforced eastern-flank defenses, recent war games in Sweden, and naval initiatives in the Baltic and Arctic, while documented gray-zone incidents such as drone incursions and airspace probes near the Baltics illustrate persistent hybrid pressure. Diplomatic contacts between Washington and Moscow, alongside Ukraine negotiations, represent the main variables that could either sustain deterrence or open windows for opportunistic moves if alliance unity appears strained.