Italy joins the Central Powers

How would World War I change if Italy joined Germany and Austria-Hungary?

The Mediterranean becomes far more contested, but logistics and geography still constrain the Central Powers.

Italy's dreadnoughts combined with the Austro-Hungarian fleet would make the Adriatic unsafe for the Allied forces historically assigned there. Supplying Gallipoli would become much harder, so that campaign might be delayed or abandoned in its familiar form. Britain and France could seek earlier Japanese help, producing the possibility of a major Mediterranean fleet action against Italian, Austro-Hungarian, and Ottoman ships. On land, the mountainous French-Italian border and Italy's own difficult supply position would create another costly front rather than an easy road into France. Italy would make the Central Powers more contiguous and dangerous, but it would not erase their broader logistical weaknesses. The Mediterranean might resemble its heavily contested Second World War role without necessarily changing the final result of the First World War.