Short answers, pulled from the story.
The siege of Jerusalem in 70 CE was the decisive confrontation of the First Jewish Revolt against Rome (66-73 CE). The revolt began after Roman procurator Gessius Florus seized temple funds in 66 CE, sparking a mass uprising. After the Roman governor of Syria was ambushed and defeated at Bethoron, the Roman general Vespasian launched a systematic campaign to suppress the revolt, with his son Titus completing the assault on Jerusalem.
Titus commanded a force estimated at a minimum of 48,200 soldiers. This combined force included four legions, V Macedonica, X Fretensis, XV Apollinaris, and XII Fulminata, along with auxiliary forces, Syrian irregulars, cavalry alae, and troops supplied by allied vassal kings. Tacitus records that a strong Arab force also joined the campaign.
Three rival faction leaders controlled different parts of the city. John of Gischala held the Temple Mount, the Ophel, and the Kidron Valley. Eleazar ben Simon initially controlled the temple's inner court before being absorbed by John's faction early in the siege. Simon bar Giora commanded the largest force and controlled the upper and lower city. The factions fought each other, burning the city's food stores, before partially uniting against the Romans.
The question remains unresolved among historians. Josephus claims that Titus tried to stop the fire after a Roman soldier ignited the temple, but most modern scholars reject this account. The fourth-century historian Sulpicius Severus, possibly drawing on Tacitus, claims Titus ordered the destruction. Historians Doron Mendels and Steve Mason interpret the destruction as intentional and ideologically motivated, with Mason noting that Rome had previously destroyed temples in Carthage and Corinth and that a laudatory poem by Valerius Flaccus celebrates Titus as scattering firebrands through Jerusalem.
The Roman official Fronto sorted survivors in the Court of the Women: rebels and brigands were executed, the tallest and most handsome were chosen for Titus's triumph in Rome, prisoners over 17 were sent in chains to Egypt, many were distributed across the empire for execution by sword or wild animals, and those under 17 were sold into slavery. Josephus reports that 97,000 were enslaved in total and that about 11,000 prisoners died of starvation while in custody. Simon bar Giora was executed at the Mamertine Prison in Rome during the triumph in 71 CE.
Vespasian completed the Temple of Peace in 75 CE, housing the menorah, the Table of Showbread, and other temple objects from Jerusalem. The Colosseum, completed under Titus, was financed according to an inscription from the spoils of the Judaean war. Emperor Domitian commissioned the Arch of Titus, still standing in the Roman Forum, whose interior reliefs depict soldiers parading the seven-branched menorah during the triumphal procession. The menorah depicted on that arch was later chosen as the emblem of Israel. A coinage campaign known as Judaea Capta was also issued over a span of 10-12 years.