Otto von Bismarck was a key Prussian statesman who unified Germany through strategic wars and maintained peace in Europe after 1871 by skillfully using diplomacy. His foreign policy aimed to isolate France while ensuring good relations with Austria and Russia, culminating in several alliances, including the Dual Alliance and the Reinsurance Treaty. However, his policies began to unravel following his resignation in 1890, leading to increased tensions and the eventual possibility of a two-front war for Germany.