The Hanseatic City of Lübeck is the second largest city in Schleswig-Holstein, in northern Germany, and one of the major ports of Germany. It was for several centuries the "capital" of the Hanseatic League ("Queen of the Hanse") and because of its Brick Gothic architectural heritage is on UNESCO's list of World Heritage Sites. In 2005 it had a population of 213,983.
Situated at the Trave River, Lübeck is the largest German port on the Baltic Sea. The old part of the town is an island enclosed by the Trave. The Elbe-Lübeck Canal connects the Trave with the Elbe River. Another important river near the town centre is the Wakenitz. Autobahn 1 connects Lübeck with Hamburg and Denmark (Vogelfluglinie). The borough Travemünde is a sea resort and ferry port at the coast of the Baltic Sea.
Although a small port-city, Luebeck was very important to Protestant forces during the Thirty Years' War. In the summer of 1633, the League of Ostend attacked Luebeck on land with a joint Danish-French army, and blockaded it at sea with French, English, and Danish fleets. The plan developed by Cardinal Richelieu was designed to cut Gustavus Adolphus off from his lifeline to Sweden by seizing or blockading the available ports. By personally reinforcing the garrison at Luebeck, Gustavus very nearly played into Richelieu's hands.
In addition to the siege and blockade at Luebeck, Richelieu had arranged for military pressure to beleaguer the Confederated Principalities of Europe from nearly every side, requiring Gustavus' army to defend in strength on multiple fronts, and preventing anything more than token reinforcements lest they suffer defeat on some other front.