Expansion of Macedonia under Philip II
The Third Sacred War (often just called 'the' Sacred War) broke out in 356 BC, and would present Philip with his first real opportunity to expand his influence into the affairs of central and southern Greece. The war was ostensibly caused by the refusal of the Phocian Confederation to pay a fine imposed on them in 357 BC by the Amphictyonic League, a pan-Greek religious organisation which governed the most sacred site in Ancient Greece, the Temple of Apollo at Delphi. Behind the religious element, there probably lay a display of "realpolitik" in bringing charges against the Phocians, instigated by the Thebans. At this time, Thebes controlled a majority of the votes in the council, and at the autumn meeting in 357 BC, the Thebans were able to have both the Phocians (for the cultivation of the sacred land) and the Spartans (for occupying Thebes some 25 years previously) denounced and fined. Since the fines for both parties were "unjustifiably harsh", the Thebans probably expected neither party to pay, and thus to be able to declare a "sacred war" on either.
Religious war
The Crusades against Muslim expansion in the 11th century was recognized as a "holy war" or "bellum sacrum" by later writers in the 17th century. The early modern wars against the Ottoman Empire were seen as a seamless continuation of this conflict by contemporaries.
The term "religious war" was used to describe, controversially at the time, what are now known as the European wars of religion, and especially the then-ongoing Seven Years' War, from at least the mid 18th century.