Ukraine’s post-war reconstruction is crucial but unmanageable without victory, a just peace agreement, or security guarantees. The conflict’s roots trace back to the 2014 Maidan Revolution and Russia’s subsequent actions, like the annexation of Crimea and the Donbas War. Russia’s inability to modernize and its leaders’ imperialist mentality led to the 2022 invasion. Russia’s war economy and ability to overwhelm with weapons and ammunition have allowed it to maintain high costs in Ukraine. Still, its relative decline is visible in economic, technological, and political realms, while changes in the international system’s balance of power limit Russia’s influence, causing aggressiveness and instability in its periphery. Any possible U.S. disengagement from Ukraine jeopardizes its hegemonic decline and increases global instability. Ukraine’s reconstruction must consider the competing regional and Euro-Atlantic security logic, balancing Ukraine’s European aspirations amid Russia’s efforts to reassert influence. The chapter examines Ukraine’s struggle, options, and implications for regional and Euro-Atlantic security. It analyses whether Russia is losing the great power competition, acknowledging that Western society has a decisive role in balancing and enhancing opportunities for Ukraine’s reconstruction, including its interconnection with Central Asia and the Black Sea region. Consequently, Ukraine’s integration into the Euro-Atlantic security architecture is critical to long-term stability.