If a President dies and the Vice President takes over, the new President would appoint a vice president, authorized by the 25th amendment.
A changing climate forced people to migrate from cold northern locations to more temperate regions.
What was the main reason for the split in the Indian National Congress at Surat in 1907? The Congress split in 1907. The Moderates were opposed to the use of boycott. They felt that it involved the use of force.
In the middle ages there was an increased trade. Mostly the establishment of what would be later called the Silk road that followed the Mongol invasions, together with an increasing bolstering of christian forces and the expansions of towns all happened during the middle ages.