Complex sentence: The tactics were similar to all other Greek hoplite battles, except that when the armies were arrayed, with the Spartans having the customary honor of being on the right, the army drifted right as it advanced.
Split into simpler sentences: The tactics were similar to all other Greek hoplite battles. Except that when the armies were arranged, with the Spartans having the customary honor of being on the right, the army drifted right as it advanced.