His admirable skill as a leader could not change the nature of his troops.

The Spanish militia retained its character, untrustworthy as the wave or the wind; now collected in masses to the number of 150,000, now melting away again to a mere handful.
The Roman emigrants, likewise, continued insubordinate, arrogant, and stubborn.

Those kinds of armed force which require that a corps should keep together for a considerable time, such as cavalry especially, were of course very inadequately represented in his army.

The war gradually swept off his ablest officers and the flower of his veterans; and even the most trustworthy communities, weary of being harassed by the Romans and maltreated by the Sertorian officers, began to show signs of impatience and wavering allegiance.

It is remarkable that Sertorius, in this respect also like Hannibal, never deceived himself as to the hopelessness of his position; he allowed no opportunity for bringing about a compromise to pass, and would have been ready at any moment to lay down his staff of command on the assurance of being allowed to live peacefully in his native land.
But political orthodoxy knows nothing of compromise and conciliation.
Sertorius might not recede or step aside; he was compelled inevitably to move on along the path which he had once entered, however narrow and giddy it might become.
The representations which Pompeius addressed to Rome, and which derived emphasis from the behaviour of Mithradates in the east, were successful.