WASHINGTON — Britain’s vote to leave the European Union comes as the 28-nation bloc is grappling with more than its usual economic issues. The union is also in the midst of deep ideological divisions over the major diplomatic and security issues of the day.

The body has traditionally been an afterthought in such matters, with individual states or the North Atlantic Treaty Organization, a strictly military alliance, taking the lead. But that is slowly changing. Britain’s departure, analysts say, could shift internal debate on not just individual issues but the very nature of the union’s role in diplomacy and security.

As France and Germany fill the leadership void, they will have an opportunity to pursue a shared goal that Britain has blocked: expanding the European Union’s integration to include military policy.

This ambition, which some union officials are already pushing forward, would expand the bloc’s ability to act as a unified diplomatic body, and allow it to put muscle behind its increasingly prominent role in the world. It would give Europe a greater ability to confront security challenges, particularly the threat that many Eastern European members perceive from Russia.