A temporal clause with cum , when , and some past tense of the Indicative dates or defines the time at which the action of the main verb occurred:— eō [lituō] regiōnēs dīrēxit tum cum urbem condidit (Div. 1.30) , he traced with it the quarters [of the sky] at the time he founded the city. cum occīditur Sex. Rōscius, ibīdem fuērunt servī ; ( Rosc. Am. 120 ), when Roscius was slain, the slaves were on the spot. [ occīditur is historical present.] quem quidem cum ex urbe pellēbam , hōc prōvidēbam animō ; ( Cat. 3.16 ), when I was trying to force him (conative imperfect) from the city , I looked forward to this. fulgentīs gladiōs hostium vidēbant Deciī cum in aciem eōrum inruēbant (Tusc. 2.59) , the Decii saw the flashing swords of the enemy when they rushed upon their line. tum cum in Asiā rēs māgnās permultī āmīserant (Manil. 19) , at that time , when many had lost great fortunes in Asia. This is the regular use with all tenses in early Latin, and at all times with the Perfect and the Historical Present (as with postquam etc.). With the Imperfect and Pluperfect the Indicative use is (in classical Latin) much less common than the Subjunctive use defined below (§ 546 ). This construction must not be confused with that of cum , whenever , in General Conditions (§ 542 ).