In Rome the three main Caesarian leaders (Antony, Octavian and Marcus Aemilius Lepidus), who controlled almost all the Roman army in the west, had crushed the opposition of the senate and established the second triumvirate.

In 42 BC, Gaius Norbanus Flaccus and Decidius Saxa were sent by the triumvirs with an eight-legion advance guard into Macedonia against the murderers of Julius Caesar.

As Marc Antony and the bulk of the triumvir's troops arrived (minus Octavian, who was delayed at Dyrrachium because of ill health), they found Amphipolis well guarded and Norbanus was left in command of the town.

[12][13] On the same day of the first battle of Philippi the Republican fleet, patrolling the Ionian Sea, was able to intercept and destroy the triumvirs' reinforcements (two legions and other troops and supplies led by Gnaeus Domitius Calvinus).

To avoid being outflanked Brutus was compelled to extend his line to the south, parallel to the Via Egnatia, building several fortified posts.

Brutus' defensive position was still secure, holding the high ground with a safe line of communication with the sea and he still wanted to keep the original plan of avoiding an open engagement while waiting for his naval superiority to wear out the enemy.

A second encounter, on 23 October, finished off Brutus's forces, and he committed suicide in turn, leaving the triumvirate in control of the Roman Republic.

Arrows or javelins were largely ignored and the soldiers packed into solid ranks fought face-to-face with their swords, and the slaughter was terrible.

Some of the nobles who were able to escape negotiated their surrender to Antony and entered his service (among them Lucius Calpurnius Bibulus and Marcus Valerius Messalla Corvinus).

Antony remained in the East, while Octavian returned to Italy, with the difficult task of finding the land to settle a large number of veterans.

However, the remaining republicans in the east rallied behind Quintus Labienus who had taken refuge in the Parthian Empire; the latter realm had supported both the Liberators as well as Pompey before them.

[1] Convinced by Labienus and the continuing unrest in the east that the Roman defenses were weak, the Parthian Empire launched an invasion in 40 BC.

The joint Parthian-Republican force initially overran much of Syria and Asia Minor, but was eventually repelled by troops loyal to the Second Triumvirate.