A sustained German-Spanish relationship could affect an 1870 war with France as well as the later Spanish-American War. Spain joining Prussia and Germany would give France another opponent. Access to Spanish ports would also provide places from which Prussian naval forces could operate. The consequence depends on the dynastic connection developing into a close political and military relationship.
Notable Point · 30:36-31:21
How Spanish ports could change a German war with France
In the Hohenzollern-Spain counterfactual, Spanish alignment could add another opponent and new naval bases to France's problems in 1870.