One of the main reasons that ancient Greece fell to Macedonia during the 4th century B.C. was the superior tactical planning employed against Greece by King Philip II of Macedon. In addition to reorganizing and strengthening the Macedonian military forces, King Philip II relied upon diplomatic strategies, bribery, trickery and the information provided by his intelligence service to gain a significant advantage over the Greek city-states. Philip II was also adept at playing his enemies against each other, and the military maxim "divide and conquer" has been credited to him.
Historians believe that Macedonians came to view themselves as members of a collective and unified territory during the time of King Philip II. This much greater sense of national identity may have contributed to the kingdom's ability to defeat the many divided and often feuding Greek city-states.
The military tactic of the phalanx assault, employing a rectangular formation of advancing troops armed with a long spear called a "sarissa," was effectively developed by King Philip II. This proved to be a decisive element in many of the victories won against the Greek city-states. Overall, the Macedonian military had been greatly improved by the time the major offenses were launched against the Greeks. The Macedonian's advanced siege techniques and greater maneuverability enabled them to easily overcome the Greek defenses.