Former President Thomas Jefferson called the Missouri crisis a "fire bell in the night," an ominous warning that slavery in the territories was an issue with the potential to ignite a national conflagration. But Congress resolved that crisis without violence through the Missouri Compromise of 1820. As a result, the issue of slavery in the territories remained more or less quiescent for almost three decades. But the acquisition of huge parcels of new land after the Mexican War reopened the issue of slavery in the territories and forced Congress to face the issue once again. The solution chosen this time, popular sovereignty , seemed acceptable under the circumstances and helped break the Congressional deadlock of the late 1840s. As subsequent events in the 1850s would quickly demonstrate, however, the sectional truce achieved in the Compromise of 1850 proved short-lived.