Who overran constantinople and ended the byzantine empire in 1453?

Why was the battle of stalingrad a turning point in the european war

Did the both the us and ussr have atomic weapons after 1949

Which of the following are characteristics of effective government leaders? select all that apply : has accumulated enough wealth to operate the government : willingness to accept responsibility : keep a government strong and active : has be a successful in the entertainment field : act as a final point of authority