Three times Severus was compelled to have recourse to arms in order to render secure the dominion of Rome in the region of the Euphrates: at the beginning of his reign (193 A.D.) when the Parthians and the Arabians of Hatra gave assistance to the rival emperor Pescennius Niger, he added to the empire the whole region between the Euphrates and the Tigris under the name of Mesopotamia. Then in 197 A.D. when he was called away to Gaul by the revolt of Clodius Albinus, those whom he had just subdued in the east arose in insurrection; after defeating Albinus (198) he returned to the east and conquered the enemy in two campaignsº 198‑199: the royal cities of the Parthians, Ctesiphon and Seleucia, were captured and 100,000 prisoners were taken and sold as slaves. However, the Romans did not succeed in capturing Hatra, the desert stronghold of the Arabians. In spite of this the emperor took the cognomina of victory Arabicus Adiabenicus (Adiabene corresponds to ancient Assyria) Parthicus Maximus. In 202 he returned to Rome and celebrated the tenth anniversary of his reign (decennalia); on this occasion the arch was erected in his honour by the Senate and the people: but he did not celebrate a triumph after his  p84 wars in the east. The excellent preservation of the arch is owing to the fact that in the middle ages the southern half of it was the property of the neighbouring church of SS. Sergio e Bacco (see fig. 10 and 42), and the northern side belonged in the twelfth century to a fortification of the barons (claustrum Cimini), remains of which (embattled tower, see fig. 35 and 56) were still in existence in the sixteenth and seventeenth centuries.

In antiquity the arch was accessible from the Forum only by steps and was accordingly not used for ordinary street traffic. The middle archway is •40 ft. 4 inches high and 22 ft. 11 inches wide; each of the side archways is •22 ft. 11 inches high and 9 ft. 10 inches wide. The façades are decorated each with four columns of composite  p85 style, standing on high bases; on the sides of these bases are bas-reliefs representing legionary soldiers leading Oriental prisoners in chains. On the keystone of the middle arch on the side toward the Capitoline is Mars; in the spandrelsº are Victories with trophies, and beneath them the Genius of summer (on the left) and that of autumn (on the right). Over the side archways, in the spandrels are river-gods, above them are narrow reliefs with approximately the same representation on all four sides; Roma (at the right end) receives the homage of conquered Oriental peoples; booty and trophies are being carried on wagons.

Above are large reliefs with scenes from the history of the war, each in  p86 two rows; over the right-hand arch (fig. 36) in the upper row: the expedition setting out, the emperor, surrounded by his suite and the standard-bearer, is making an address (allocutio) from a raised platform (suggestus); in the lower row: the besieging of a city, the walls of which are being destroyed by a battering-ram (aries).

Over the left-hand arch (fig. 37) in the upper row: the siege of a city situated on a river (Euphrates or Tigris?), the inhabitants are sending a deputation to the emperor announcing their submission; in the lower row: a city or a stronghold, as near a river, being besiegedº by the Romans who are also putting to flight the enemy's cavalry. There are similar bas-reliefs on the side toward the Forum: in the spandrels the Genius of spring (on the right) and that of winter (on the left); over the left arch: beginning of the expedition and address of the emperor; over the right arch: a parley with the barbarians, making of a camp, storming of a city. A more accurate description is not possible, both on account of the fragmentary character of our knowledge of the actual events, and also because of the schematic treatment, which when compared with the life-like and individual scenes on the column of Trajan or even on that of Marcus Aurelius shows clearly the rapid decline of art at the end of the second century.

Fig. 38. Coin of Severus.

On the attic, the corner pillars of which were adorned with bronze ornaments (trophies?), is the inscription, according to which the senate and the people dedicated the arch to Severus and Caracalla "on account of the restoration of the state and the extension of the empire". Examination shows that the last two letters P(atri) P(atriae) of the third line and the whole fourth line occupy the place of an older inscription which has been erased — the surface on which the letters now visible were cut is not in the surface plane of the rest of the inscription, because  p87 in erasing the original inscription the marble was cut away. The rivet-holes for the bronze letters of the original inscription are still to be seen, so that the letters can be deciphered with certainty: ET P. SEPTIMIO GETAE NOB(ilissimo) CAESARI. After Caracalla in the year 211 had by murder rid himself of his brother, who had been appointed his partner on the throne, he caused his name to be erased from all public monuments. The lacuna thus created was filled up adding to the titles of Severus and Caracalla the phrase: P(atri) P(atriae) OPTIMIS FORTISSIMISQVE PRINCIPIBVS. "To the father of the fatherland, to the best and bravest of rulers". According to the coins a six-horse chariot stood in the middle of the attic, with the statues of Severus and his sons, and at the corners possibly in addition equestrian statues.

On the side toward the Forum there seems to have been originally a flight of 6‑8 steps in front of the whole width of the arch; later for reasons which we do not know the level of the Forum was lowered at this point by •about eight feet. As a result of this the flight of steps had to be lengthened, and in the side arches it is still possible to see how steps were cut into the great travertine blocks of the foundation. On account of this  p88 change of level the foundation of travertine which had been originally under the ground came into view at the corners and was in its turn covered with thick slabs of white marble, in order to make it harmonize with the rest of the structure, which was entirely of marble.

See: CIL. VI, 1033 (=Dessau 425). — Rossi Archi trionfali T. 50‑59; Jordan I, 2, 213; Lanciani 284; Huelsen, R. M. 1902, 21; Vaglieri 151.