The European Union reacted quickly to Russia's invasion of Ukraine by offering financial and military support, reviving EU enlargement, and recognizing Ukraine as a future EU candidate. This move marked a significant shift in Ukraine's aspirations to join the EU, but came at the cost of a brutal war with Russia. The EU's response to the war showed both its strengths and limitations as a geopolitical actor. While the EU initially showed promise in supporting Ukraine, it struggled to increase defence capacities and reform decision-making in key areas. The EU's recognition of Ukraine as a future candidate reflected its past use of enlargement as a foreign policy tool. The war has triggered a revival of the enlargement process for Ukraine, Moldova, Georgia, and other candidates in the Western Balkans.