An Octavian Chronicles Map.
Antony and his army marched in from the west. He set up camp about a mile away from Cassius’s hill. Octavian and his army had not yet arrived because he was ill and still back at the port city of Dyrrachium on the coast of Illyricum (current Albania). It was at this point that Brutus and Cassius had their best chance to defeat Antony. They held a superior position with a superior number of men, but they didn’t attack. Octavian arrived several days later and set up his camp opposite Brutus’ hill.
In this first battle, Antony defeated Cassius and Brutus defeated Octavian. Cassius commited suicide after retreating to Philippi at a time when it was not clear whether Brutus had won or lost. Some speculated that he did it because he thought he’d lost, and therefore all was lost. Others speculated that he did it for one of two other reasons; that he realized Brutus had won and his pride would not let him be second to him, or that he could not live with himself for not having attacked Antony when he held the superior advantage.
For his part, Octavian was not in his camp when Brutus’ army attacked. Recovering from his illness, he’d been carried away to a safe place in the woods and placed on a makeshift bed. Had he been in his camp, he would’ve been killed because the enemy soldiers quickly destroyed his tent, thinking he was in it. There has been a question as to whether he was sick from a physical illness or sick from a fear of being in battle. Whatever the truth may be, the same historical record that raises this suspicion has him heavily engaged in the Second Battle of Philippi which occurred three weeks later.