Thessaly and the Sacred War (356–352 BC)
I pulled most of this from Wikipedia, so lets take it with a grain of salt. I post as I am a bit confused about who fought with whom. The situation is decidedly unclear and my scenario for this (non GMT) also seems buggered. So this is all we get…. No battle report for Thessaly. On to the next segment of the campaign, where we will conduct the Battle of Crocus Plain or Field.
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 facade, 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.
The ruins of ancient Delphi
In response, the Phocians, under the leadership of Philomelos, seized Delphi (which was situated within the boundaries of Phocis), and asserted the ancient claim of Phocis to the presidency of the Amphictyonic League, intending to annul the judgment against themselves. There seems to have been some sympathy in Greece for the Phocians, since other states could see that “the Thebans…had used the Amphictyony to pursue petty and destructive vendettas”. The Phocians were supported by Athens (perennial enemies of Thebes) and unsurprisingly Sparta, who hoped to see their own fine wiped out when the Phocians seized Delphi. However, Philomelos plundered the treasury of Apollo to pay for mercenaries, thus raising a powerful army, but drastically altering the opinion of the other Greek states. In winter 356/355 BC, a “sacred war” was declared against the Phocians by the Amphictyonic council, with the Thebans being the major protagonists. The war started relatively well for the Phocians, but a severe defeat was inflicted on the Phocians at Neon by the Thebans in either 355 or 354 BC, and Philomelos was killed. Undeterred, Onomarchos took over the Phocian effort, and raised new mercenaries to carry on the fight.
The ancient sources for the sacred war are scant, and generally lacking in firm chronological information. The most we know that is concrete is that it is generally accepted that the war lasted 10 years, and ended in summer 346 BC .
Disregarding the dates, most historians agree upon the same sequence of events for this part of the Sacred War.
First campaign in Thessaly
The Sacred War appears to have laid way for renewed conflict within Thessaly. The Thessalian Confederation were in general staunch supporters of the Amphictyonic League, and had an ancient hatred of the Phocians. Conversely, Pherae had allied itself with the Phocians. In either 354 or 353 BC the Aleuadae appealed to Philip to help them defeat Pherae. Philip responded positively, perhaps unsurprisingly:
…the struggle between Pherae and its neighbours offered Philip rich possibilities. The chronic political instability of the area and the support of the Thessalian confederation guaranteed that he would face no united opposition to his ambitions. The Thessalians were giving Philip the same opportunity to become ascendant there that they had given Pelopidas and the Thebans in 369 BC.
— John Buckler, 
Philip thus brought an army into Thessaly, probably with the intention of attacking Pherae. Under the terms of their alliance, Lycophron of Pherae requested aid from the Phocians, and Onormarchos dispatched his brother, Phallyos with 7,000 men;however, Philip repulsed this force before it could join up with the Pheraeans. Onomarchos then abandoned the siege he was currently prosecuting, and brought his whole force into Thessaly to attack Philip. It is possible that Onomarchos hoped to conquer Thessaly in the process, which would both leave the Thebans isolated (Locris and Doris having already fallen to the Phocians), and give the Phocians a majority in the Amphictyonic council, thus enabling them to have the war declared over.Onomarchos probably brought with him 20,000 infantry, 500 cavalry, and a large number of catapults, and outnumbered Philip’s army. The exact details of the campaign that followed are unclear, but Onomarchos seems to have inflicted two defeats on Philip, with many Macedonians killed in the process. Polyaenus suggests that the first of Onomarchos’s victories was aided by the use of the catapults to throw stones into the Macedonian phalanx, as they climbed a slope to attack the Phocians. After these defeats, Philip retreated to Macedon for the winter. He is said to have commented that he “did not run away but, like a ram, I pulled back to butt again harder”.
Second campaign in Thessaly
Philip returned to Thessaly the next summer (either 353 or 352 BC, depending on the chronology followed), having gathered a new army in Macedon. Philip formally requested that the Thessalians join him in the war against the Phocians; the Thessalians, even if underwhelmed by Philip’s performance the previous year, realistically had little choice if they wanted to avoid being conquered by Onomarchos’s army. Philip now mustered all the Thessalian opponents of Pherae that he could, and according to Diodorus, his final army numbered 20,000 infantry and 3,000 cavalry.
At some point during his campaigns in Thessaly, Philip captured the strategic port of Pagasae, which was in effect the port of Pherae. It is unclear whether this was during the first or second campaign; both Buckler and Cawkwell suggest that it took place in the second campaign, before the Battle of Crocus Field. By taking Pagasae, it is possible that Philip prevented Pherae from being reinforced by sea during his second campaign. Buckler suggests that Philip had learnt his lesson from the previous campaign, and internded to cut Pherae off from outside help before attacking it.
Battle of Crocus Field
Main article: Battle of Crocus Field
Meanwhile, Onomarchus returned to Thessaly to try and preserved the Phocian ascendancy there, with approximately the same force as during the previous year. Furthermore, the Athenians dispatched Chares to help their Phocian allies, seeing the opportunity to strike a decisive blow against Philip. Subsequent events are unclear, but a battle was fought between the Macedonians and the Phocians, probably as Philip tried to prevent the Phocians uniting forces with the Pheraeans, and crucially, before the Athenians had arrived. According to Diodorus, the two armies met on a large plain near the sea (the ‘crocus field’), probably in the vicinity of Pagasae. Philip sent his men into battle wearing crown of laurel, the symbol of the Apollo; “as if he was the avenger…of sacrilege, and he proceeded to battle under the leadership, as it were, of the god”. Some of the Phocian mercenaries supposedly threw down their arms, panged by their guilty consciences. In the ensuing battle, the bloodiest recorded in ancient Greek history, Philip won a decisive victory against the Phocians. In total, 6,000 Phocian troops had been killed including Onormarchos, and another 3000 taken prisoner. Onomarchos was either hanged or crucified and the other prisoners drowned, as ritual demanded for temple-robbers. These punishments were designed to deny the defeated an honourable burial; Philip thus continued to present himself as the pious avenger of the sacrilege committed by the Phocians.Buckler states that: “Nor should one automatically assume that a mass-drowning…would shock the Greek world. Even the mild-tempered Isocrates felt that the Phocian mercenaries were better off dead that alive…Dreadful indeed was the punishment, but it was entirely consistent with Philip’s role as Apollo’s champion”.
Re-organisation of Thessaly
It was probably in the aftermath of his victory (if not before) that the Thessalians appointed Philip Archon of Thessaly. This was an appointment for life, and gave Philip control over all the revenues of the Thessalian Confederation, and furthermore made Philip leader of the united Thesslian army.
Philip was now able to settle Thessaly at his leisure. He first probably finished the siege of Pagasae, to deny the Athenians a landing place in Thessaly. Pagasae was not part of the Thessalian Confederation, and Philip therefore took it as his own, and garrisoned it. The fall of Pagasae now left Pherae totally isolated. Lycophron, rather than suffer the fate of Onomarchos, struck a bargain with Philip, and in return for handing Pherae over to Philip, he was allowed, along with 2000 of his mercenaries, to go to Phocis. Philip now worked to unite the traditionally fractious cities of Thessaly under his rule. He took direct control of several cities in western Thessaly, exiling the dissidents, and in one case refounding the city with a Macedonian population; he tightened his control of Perrhaebia, and invaded Magnesia, also taking it as his own and garrisoning it; “when finished, he was lord of Thessaly.”