How was Jerusalem destroyed in 70 AD?

20. And when ye shall see Jerusalem compassed with armies, then know that the desolation thereof is nigh.

21. Then let them which are in Judea flee to the mountains; and let them which are in the midst of it depart out; and let not them that are in the countries enter thereinto. (Luke 21:20-21)

(The following is taken from the LDS Institute Pearl of Great Price Student Manual, phone download app version):

“Because of the nature of the (Jerusalem) temple’s construction, the prophesy of its destruction, (that occurred in 70 AD) may have seemed nearly impossible to the Jews. Elder Bruce R. McConkie, then a member of the Seventy, wrote: ‘Some single stones were about 67 and ½ feet long, 7 and ½ feet high and 9 feet broad; the pillars supporting the porches, all one stone, were some 37 and ½ feet tall. It is said that when the Romans destroyed and ploughed Jerusalem, six days battering of the walls failed to dislodge these mighty stones. The temple was, of course, finally leveled to the ground and…the stones were rooted out and scattered elsewhere and so was a once secure and great nation.” (Doctrinal New Testament Commentary, 3 vols. [1966-73], 1:637).

“The wickedness of the Jews at Jerusalem persisted and increased after the Resurrection of the Savior, setting the scene for the destruction that Jesus prophesied. Elder Ezra Taft Benson, then a member of the Quorum of the Twelve Apostles, referring to a history written by Will Durant, said: ‘The siege of Jerusalem under Titus [lasted] for 134 days.

(Hunger exceeded human endurance, blood flowed in the streets), during which 1,110,000 Jews perished and 97,000 were taken captive;…the Romans destroyed 987 towns in Palestine and slew 580,000 men and a still larger number, we are told, perished through starvation, disease and fire.’(Conference Report, Apr. 1950, 74).

‘Thousands [of Jews] were carried off to Egypt to work in the quarries and mines as lifelong slaves. Boys and women were sold to slave traders and thousands of others died of starvation in the prison camps. A remnant of this conquered people was scattered to the ends of the earth’ (H. Donl Peterson, “The Fall of Jerusalem,” Ensign, May 1972, 42)

“The suffering of the Jews following the death and Resurrection of Christ was clearly prophesied by Nephi and Jacob in the Book of Mormon (see 1 Nephi 19:14; 2 Nephi 6:9-11; 10:3-6; 25:9-16). (But what of the Jews who heeded Jesus’ warning and fled in haste? Guided by Revelation, as true saints always are, they fled to Pella in Perea and were spared.

Historical events, such as the Crusades, the Inquisition and the Holocaust, are other times since A.D. 70 when the Jews have been persecuted and destroyed.”

37. O Jerusalem, Jerusalem, thou that killest the prophets, and stonest them which are sent unto thee, how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings, and ye would not! (Matthew 23:37)