What event occurred in the nearly two-year time span between act 3 and act 4 of the tragedy of Julius Caesar?

Between acts 3 and 4, two years passed in the play "Julius Caesar. After the two years of the death of Julius Caesar Mark Anthony, Lepidus, and Octavius formed the Second Triumvirate. They recruited and sent an army against Brutus and Cassius. Their army was much strong and ready as compared to the Brutus and Cassius'. Brutus and Cassius' friendship came to an end in the act thereby leading to their fall.