This picture is historically inaccurate. Judging from their helmets and armors (loricae squamatae), these Roman cavalry are of the 1st to 2nd century AD (cf. pp. 17-20 and 24 of Simkins). On the other hand, according to several sources, iron stirrups, which are thought to have been invented in China or Central Asia, weren't introduced to the West until at least the late 6th century AD, and thus ancient Romans never used them (see p. 130 of Penn et al., Hemming, Arndt, etc.). In addition, Roman cavalry didn't use gladii as depicted in the picture. They in reality used spathae (sword double-edged like gladius but longer and narrower) instead (see p. 22 of Simkins).

Holy anachronism Batman !

lyagushka said:

...In addition, Roman cavalry didn't use gladii as depicted in the picture. They in reality used spathae (sword double-edged like gladius but longer and narrower) instead (see p. 22 of Simkins)...

Yup, using a short, infantry gladius from a horse's back would be quite troublesome. That's why cavalry swords are longer: to reach farther.

Asqo said:

Yup, using a short, infantry gladius from a horse's back would be quite troublesome. That's why cavalry swords are longer: to reach farther.

....and lances are even superior to long swords when used by cavalry.