What are the three major security challenges Europe currently faces?

Europe is currently confronting three interconnected security challenges: a potentially weaker NATO alliance, an emboldened Russia, and deepening rifts within the European Union regarding appropriate responses to these threats. These divisions appear to be particularly concerning as they emerge during a critical period when unified action would be most effective against external pressures. With concerns about possible U.S. troop withdrawals and ongoing conflict in Ukraine, European leaders are struggling to develop a cohesive defense strategy amid this complex geopolitical landscape.