それから数十年間軍団は一部の属州で援軍のような働きをしており、[[3世紀]]の絶え間ない玉座をかけた戦いでは先兵としてあり続けた。[[ガッリエヌス]]は軍団に対して「クィンキエス・フィレリス・クィンキエス・ピア（V Fidelis V Pia-『五たび忠実で五たび誠実な軍団』の意）」と「セクシエス・フィデリス・セクシエス・ピア（VI Fidelis VI Pia - 『六たび忠実で六たび誠実な軍団』の意）の称号を授けられている。
この称号が授けられた時、軍団はどこに駐在していたのかはわかってはいない。<!-- ここから訳が怪しいです -->考えうる他の条件が同じだとすると、[[ウァレリアヌス]]と息子であり共同統治者の[[ガッリエヌス]]は[[250年代]]末にはこの軍団を東に連れて行く考えだったのかもしれない。もしそうなら軍団は[[シャープール1世]]によって敗北、ウァレリヌスとともに捕囚の憂き目に巻き込まれていただろう。しかし[[マクリアヌス]]の反乱や[[ゼノビア]]の[[パルミア]]の半独立勢力など、引き込まれるであろう次々と迫る危険を第2軍団が回避できたという事、またはガッリエヌスから敬意ある継承を贈られたという事から察すると、軍団は父親のウァレリアヌスではなく、ガッリエヌスの指揮下にあったものと考えられる。しかしながら、可能性は低いものの、叛乱者マクリアヌスの指揮下にあって敗北、ガッリエヌスによって赦され帝国内に戻っていた可能性も否定できない。
<!-- ==Parthian campaign and Castra Albana (197-4th century)=
Together with its twin legions [[Legio I Parthica|I ''Parthica'']] and [[Legio III Parthica|III ''Parthica'']], the Second Parthian legion was levied for the attack on the eastern frontier. The campaign was a success and [[Ctesiphon]], the Parthian capital was taken and sacked. After this war, II ''Parthica'' returned to [[Italia (Roman province)|Italia]], and was stationed near Rome, in ''Castra Albana''<ref>For this reason, the legion was also known as "Albanian legion".</ref> ([[Albano Laziale]]) – it was the first legion stationed in Italia in the last two centuries. Since it was not garrisoning a [[Roman province]], they functioned both as a reserve that could be used in afflicted parts of the [[Roman Empire|Empire]], as well as a security element against possible internal rebellions. Emperors in the 3rd century were very likely to have problems with usurpers, and Severus, by stationing the II ''Parthica'' near the capital, was aware of it.
Nevertheless, the legion served in the Severan campaign in Britain of 208–211 and afterwards, under [[Caracalla]] against the Germanic tribe of the [[Alamanni]] in 213. Next, the legion was again sent to Parthia and their commander [[Macrinus]] was responsible for Caracalla's murder in that region in 217. In the following year, however, the II ''Parthica'', stationed in [[Apamea (Syria)|Apamea]] ([[Syria (Roman province)|Syria]]), abandoned Macrinus and sided with [[Elagabalus]]; the Second supported Elagabalus' rise to purple, defeating Macrinus in the [[Battle of Antioch (218)|Battle of Antioch]]. The new emperor awarded the legion with the cognomina ''Pia Fidelis Felix Aeterna'' (forever faithful, loyal and pious).
===Under Severus Alexander and Maximinus===
In 231, the legion fought under [[Alexander Severus]] against the [[Sassanid Empire]], and returned with the emperor to the German provinces. It was at ''Moguntiacum'' (modern [[Mainz]]), when Alexander was assassinated in 235. In the following fight for the power, the II ''Parthica'' sided with [[Maximinus Thrax]]. In 238, the [[Roman senate]] declared Maximinus ''persona non grata'' and nominated [[Gordian III]] as emperor. Maximinus then marched on Rome to fight for his rights, taking the II ''Parthica'', among other legions, with him. What happened next is a good example of the political power of the legions in the 3rd century. The II ''Parthica'' weighted the chances of its commander and, concluding that supporting him was not a good move, they killed Maximinus before he could harass the senate. As a reward, they were pardoned for supporting a public enemy and allowed to return to their base and families in the Alban mountains. -->
In the next decades they were used as reinforcements in several provinces within the empire and continued to be used as pawns in the constant battles for the imperial throne of the 3rd century. Emperor [[Gallienus]] (253-268) awarded the legion with the titles ''V Fidelis V Pia'' and ''VI Fidelis VI Pia'' (respectively, "Five" and "Six times loyal and faithful").
Where the legion was based when it received these titles from Gallienus is uncertain. 「Other things being equal one would have thought that [[Valerian (emperor)|Valerian]], father and co-regent with Gallienus, would have wanted to take it to the east with him in the late 250s」 and that it would have been involved in his defeat and capture by King [[Shapur I|Sapor]]of the Persians at Edessa in 260. Since it continued as a functioning unit and avoided the subsequent pit-falls of over-identification with the rebellion of the [[Macrianii]] and [[Palmyra]]'s bid for autonomy under [[Zenobia]], and given the honorific title appearing on coins of Gallienus, it is probable that it was under the command of Gallienus, not his father. However unlikely, it is possible that it would have returned to Europe as part of the army of the Macrianii and was forgiven by Gallienus after the latter were defeated. Besides an inscription from Macedonia giving thanks to the god Jupiter for the safety and well-being, "pro salute et incolumitate," of Gallienus, and an inscription dated 242 CE from Rome giving thanks to the legion's "Genius Gordiana and to Fortuna" for keeping safe emperor Gordian and his spouse, there is little known regarding its fortunes in this period.<ref name=piacoins />