The only real opposition which Caesar encountered in his progress toward Rome was from him.

Domitius had crossed the Apennines at the head of an army on his way northward to supersede Caesar in his command, and had reached the town of Corfinium, which was perhaps one third of the way between Rome and the Rubicon.
Caesar advanced upon him here and shut him in.
[Sidenote: Caesar's treatment of Domitius.] After a brief siege the city was taken, and Domitius and his army were made prisoners.

Every body gave them up for lost, expecting that Caesar would wreak terrible vengeance upon them.

Instead of this, he received the troops at once into his own service, and let Domitius go free.
[Sidenote: Dismay at Rome.] [Sidenote: Pompey's distress.] In the mean time, the tidings of Caesar's having passed the Rubicon, and of the triumphant success which he was meeting with at the commencement of his march toward Rome, reached the Capitol, and added greatly to the prevailing consternation.

The reports of the magnitude of his force and of the rapidity of his progress were greatly exaggerated.