6 A second sign. And you shall hear of wars and rumours of wars. Is there then at this time war between Persians and Romans for Mesopotamia, or no? Does nation rise up against nation and kingdom against kingdom, or no? And there shall be famines and pesti lences and earthquakes in various places. These things have already come to pass; and again, And fearful sights from heaven, and mighty storms. Watch therefore, He says; for you know not at what hour your Lord does come.
Source: Catechetical Lectures (New Advent)