 Carranza was the first president under the 1717 Constitution but he was overthrown by his former ally Álvaro Obregón in 1919.Obregón took over the presidency in late 1920 and effectively applied the Constitution's anticlerical laws only in areas in which the Church was the weakest.The uneasy truce with the Church ended with Obregón's 1924 handpicked succession of the atheist Plutarco Elías Calles.