Why might governments put up walls on their borders?

Write about 50 words explaining whether or not this passage supports that explanation.in the introduction, you heard genghis khan’s explanation of why the mongols were successful conquerors in his time. the mongols were illiterate . . and perhaps no more than 700,000 in number. . they were herdsmen on the grassy plains north of the gobi desert, south of siberia’s forests. before the year 1200, the mongols were fragmented, moving about in small bands headed by a chief, or khan, and living in portable felt dwellings. the mongols endured frequent deprivations [hardships] and sparse areas for grazing their animals. they frequently fought over turf, and during hard times, they occasionally raided, interested in goods rather than bloodshed.