Although researchers have long considered the impact of the Thirteen Years’ War on the Teutonic Order’s coinage in Prussia, Polish coins were studied completely separately from the events of the war. In this paper we attempt to change this approach. In Prussia, after a war debasement, the ‘good shilling’ was restored in the years 1415–16, as a coin containing 0.87g of pure silver. The restoration was not complete because the former official shilling standard was higher. In 1407, it contained c.1.17g of pure silver. The new ‘good shilling’ most probably referred to an actual average standard of circulating old coins regarded as ‘good coinage’, in contrast to debased coinage struck between 1410 and 1414. These new ‘good’ shillings were marked with a long cross on their two faces. New bracteate pfennigs of the Third Greek cross type were also introduced, containing 0.062g of pure silver and equal to a twelfth part of a ‘good’ shilling. The ‘base’ or ‘old’ shillings, however, were not removed from circulation and a rate of 1:2 between old and new coinage was formed. Because of the lack of silver, the number of good shillings was insufficient and base shillings actually prevailed in circulation, although they were not minted any more. Prussian mints struck mostly pfennigs and, sporadically, good shillings according to the law of 1416. It was Grand Master Ludwig von Erlichshausen (1450–1467) who behaved differently. In secrecy, he reduced the silver content of shillings from 508/1000 to 342/1000 or even less. The change was possibly accomplished gradually and the last stages of the debasement took place during the Thirteen Years’ War. When the war broke out in the spring of 1454, the king of Poland granted the Prussian Confederationthe coinage rights. As the mint seats, four large cities were indicated: Toruń, Gdańsk, Elbląg and Königsberg. A mint standard had not been precisely defined but the local monetary system had been generally indicated. The new estates’ shillings were coined in Toruń only, and their standard, although uneven, was close to the earliest shilling as ordered by Grand Master Winrich von Kniprode in 1380. Such a high standard could not be upheld. After the three former cities were granted minting rights in 1457, they went back to the pre-1416 standard called the ‘old’ or ‘base’ shilling but alongside ‘new’ pfennigs. This formed a new basic Prussian monetary rate: one ‘old’ shilling was equal to six pfennigs. The Teutonic Order, having lost its main mint in Toruń, arranged another one in Malbork. Malbork was also lost in 1456 and the mint was moved to Königsberg where it stayed until the end of the Teutonic Order’s rule and beyond. The coinage debasement was soon revealed and eventually Master Ludwig reduced his Königsberg shilling’s official value by half in 1460 and made it equal to ‘old’ or ‘base’ shillings. Pfennigs minted during the war were withdrawn from circulation and the old pfennig standard was restored. Shillings struck from 1460 were ‘old’ or ‘base’ shillings and they were devoid of the long cross. The restored pfennigs were bracteates with the eagle shield. In the Kingdom of Poland a huge amount of small pennies was minted from 1430 up to the death of King Vladislas III at Varna in 1444. This coinage was intended to finance the unsuccessful war for the Bohemian crown in 1437–8 and the victorious albeit long war for the Hungarian crown, which began in 1440. The pennies were declared legal tender for all payments and they replaced larger coins, first of all, half-groat coins, in circulation. The official rate was 9 pennies = 1 half-grosz. It was believed that the Cracow mint was re-opened as late as in 1456 and minted few half-grosz coins. This was based on a misunderstanding of the evidence, both documentary and numismatic. In the early stage of the war – which was not prepared from a financial perspective – the Polish side apparently counted on the funds of rich Prussian cities. These resources were not sufficient and, seeing the protracted war, the general assembly in Łęczyca agreed to open the mint in January 1455, in order to strike half-grosz and pennies for warfare expenditure. This was certainly done if Stanisław Morsztyn, a renowned financier and merchant, was acting as mint master in March 1456. Two months later, however, King Kazimierz IV appointed five other mint masters, apparently being unsatisfied with Morsztyn’s work. The volume of coinage increased and three years later at the general assembly in Piotrków, the opposition leader, Jan Rytwiański, accused the king of ‘shattering us with very light and unjust coinage as with ordinary arson’. However, we have no evidence about a decrease in the rate of Polish coinage from that time – this happened as late as in 1479. The Polish coins which were struck then, were similar not to preceding coinage of Vladislas III but to the much older, ‘good’ coins of Vladislas II Jagiełło from c.1400, both pennies and half-grosz coins. The standard of the new coins was probably also similar to that of the old ones, as far as the former are compared with worn out coins remaining in circulation during the 1450s. Despite a small volume of half-grosz coinage, caused by the shortage of silver, this ‘good’ coinage supported the rate of pennies and eventually contributed to the king’s victory, saving his kingdom from debasement.