Why was Rome Forced to declare war on Marc Anthony?

Rome was forced to declare war on Marc Antony primarily due to his growing power and controversial actions following the assassination of Julius Caesar. After forming an alliance with Cleopatra and declaring himself king, Antony's ambitions were perceived as a direct threat to the Roman Republic. Additionally, his conflict with Octavian, Caesar's adopted heir, escalated tensions, leading to the breakdown of their political alliance and ultimately to open warfare. The declaration of war was seen as necessary to protect the Republic from what was viewed as Antony's tyranny.