I have read somewhere that due to the fertile pasture that ancient Macedonia and Thessaly share that allow for more breeding of horses, yet considering their conflicts with the Greek city-state which favour hoplite why did Macedonia or Thessaly feel the need to field such expensive and time-consuming calvary who were formed by their aristocrat and ruling elite no less?
To my rudimentary understanding of ancient warfare, calvary relied on breaking formation of their foes and run them down, yet the hoplite offers precisely the opposite. Masses of spearmen tightly pack together to form a wall of spear essentially, is this not a perfect counter to all calvary?
It is true that the broad alluvial plains of Thessaly and Lower Macedonia lended themselves to traditions of horsemanship. Indeed, Thessalian horses were considered the best in the Greek world. As for the class of the cavalry, this was simply due to the same reasons as in the other Greek city-states: the costs of maintaining even a single horse were more than most could afford, hence the cavalry was largely the preserve of the wealthier classes.
As for the Greek phalanx, it is true that it was a formation that was resilient against frontal cavalry attacks. However, the key work here is ‘frontal’. The phalanx was very vulnerable to attacks from the flanks and rear by anyone, but especially cavalry. In the Greek heartland, the threat of cavalry was not as significant due to the mountainous terrain and the resulting emphasis on heavy infantry. What cavalry there was was also not heavy or shock cavalry either. So essentially there was a deficiency in traditional Greek warfare that was not really exposed within Greece itself.
When Phillip II of Macedon built his army, he combined the strong cavalry traditions of Macedonia and Thessaly with the heavy infantry tradition of the Greek heartland, perfected in the form of his phalangites (as opposed to Greek hoplites). The Macedonian phalanx was superior to its Greek counterpart. However, it is important to understand that these two branches of the army were designed to work in concert. The phalanx was the anvil against which the enemy infantry would be pinned while the heavy cavalry wheeled around the flanks to deliver the hammer blow from behind. This was, in essence, the first recognised example of the modern military principle of ‘combined arms’.
The effectiveness of Philip’s army is among the most factors in Alexander the Great’s success. When he invaded the Persian Empire he did so with not only the finest heavy cavalry and the best heavy infantry, but an army in which those to branches worked together in concert.