Cataphract, Clibanarii, whatever, against Infantry

[marka]

I think the campaign Byron's thinking of is the series of battles conducted by Antony's lieutenant Ventidius Bassus against the Parthians in Syria, c38BC. Dio describes three battles, all Roman victories, and makes specific reference to Parthian armoured cavalry. In two cases, Ventidius uses terrain to his advantage:

…[The Parthians] imputed sloth and weakness to the Romans and therefore marched against their camp, although it was on high ground, expecting to take it without resistance. But when a sally was suddenly made, the assailants, being cavalry, were driven back down the slope without difficulty; and although at the foot they defended themselves valiantly, the majority of them being in armour, yet they were confused by the unexpectedness of the onslaught and by stumbling over one another and were defeated by the heavy-armed men and especially by the slingers; for these struck them from a distance with their powerful missiles and so were exceedingly difficult for them to withstand. Dio, Book 49.20

These accounts do, however, suggest that the Parthians were willing to send heavy cavalry on frontal assaults against infantry positions - although perhaps, with the heavy losses they suffered, they rapidly learned from their mistakes!
- Nathan

reading between the lines the parthians MAY have believed he had 'stolen a march' on their army.

to answer the original question well trained and drilled infantry in appropriate formation in a defensible position had little to fear from heavy cavalry like cataphracts provided they held their nerve...this is shown repeatedly throughout history.