information:extraction
Economic power and defense

The Hanseatic League, at first the merchant hansas and eventually its cities, relied on power to secure protection and gain and preserve privileges. Bandits and pirates were persistent problems; during wars these could be joined by privateers. Traders could be arrested abroad and their goods could be confiscated. The league sought to codify protection; internal treaties established mutual defence and external treaties codified privileges.

Many locals, merchant and noble alike, envied the League's power and tried to diminish it. For example, in London, local merchants exerted continuing pressure for the revocation of privileges. Most foreign cities confined Hanseatic traders to specific trading areas and their trading posts. The refusal of the Hansa to offer reciprocal arrangements to their counterparts exacerbated the tension.

League merchants used their economic power to pressure cities and rulers. They called embargoes, redirected trade away from towns and boycotted entire countries. Blockades were erected against Novgorod in 1268 and 1277/1278. Bruges was pressured by temporarily moving the Hanseatic emporium to Aardenburg from 1280 to 1282, from 1307 or 1308 to 1310 and in 1350, to Dordt in 1358 and 1388, and to Antwerp in 1436. Boycotts against Norway in 1284 and Flanders in 1358 nearly caused famines. They sometimes resorted to military action. Several Hanseatic cities maintained their own warships and in times of need, repurposed merchant ships. Military action against political powers often involved an ad hoc coalition of stakeholders, called an alliance (tohopesate).

As an essential part of protecting their investments, League members trained pilots and erected lighthouses, including Kõpu Lighthouse. Lübeck erected in 1202 what may be northern Europe's first proper lighthouse in Falsterbo. By 1600 at least 15 lighthouses had been erected along the German and Scandinavian coasts, making it the best lighted coast in the world, largely thanks to the Hansa.