Miguel Conde Pazos has written extensively about the diplomatic relations between Poland and Spain and the Holy Roman Empire under the House of Habsburg (Casa de Austria). The bibliography of the work reviewed includes ten of his articles on this subject. This work is the summation of many years of research on the dynamics and strategic interests that influenced the development of the diplomatic relations between the Polish Vasa and the Habsburgs from 1635 to 1668.

He analyzes in this monograph personal circumstances that affected those diplomatic relations, such as the interest of the Polish Vasa in keeping relations with the Spanish Habsburgs because of the position of the king of Spain as king of Naples, where they had landed properties, and rights to interest on a loan made to King Philip II of Spain (r. 1556–98) by their ancestor the Polish queen-consort Bona Sforza (1494–1557), grandmother of Sigismund III (1566–1632), the first Vasa who reigned in Poland. According to Conde Pazos, the relations between Poland and the Habsburgs in Spain were undermined by institutional obstacles as well as by distance. Foremost among those obstacles, he considers the electoral nature of the Polish monarchy. Spanish observers at the Polish court criticized the lack of authority of Polish monarchs, whose decisions could be discussed and abrogated by the Polish Sejm (parliament). Polish opinion of Spain reciprocated in criticizing the Spanish political system as tyrannical.

The first chapter, “La tierra de los sármatas” (The land of the Sarmatians), functions as an introduction to the relations of the Habsburgs and the Polish Vasa before 1635, including the origins of Queen Bona Sforza's heritage in the Kingdom of Naples and the aspirations of Central European princes of the Habsburg dynasty to the elective Polish crown after the death of the last king of the Jagiellon dynasty in 1572. This chapter includes a thorough analysis of the new constitution in Poland following the formal union of the Kingdom of Poland with the Grand Duchy of Lithuania at Lublin in 1569. Predominant in the new constitution was the Liberum Veto, which allowed a single member of the Sejm to veto any decision. After the establishment of the Union of Lublin regime, any decision of a king could be discussed and abrogated by the Sejm. Concerning the Liberum Veto, Conde Pazos stresses the fact that it did nothing to benefit those who today we consider “the people”—that is, plebeian social groups such as artisans, journey men, and serfs—because the Polish Sejm was a representative body of the titled nobility and the gentry.

The main subject of the book, an analysis of the relations between the Catholic dynasties of the Polish Vasa and the Habsburgs in Spain and the empire, is developed in two parts. The first part analyzes the development of a Catholic dynastic alliance starting with a rapprochement in 1589 by King Sigismund III (r. 1566–1632) as king of Poland and Sweden with the House of Habsburg, which included the support of King Philip II of Spain, and was sealed by the marriage of Archduchess Anne with King Sigismund. This dynastic union blossomed under the reign of Sigismund III's oldest son, King Wladislaw IV (r. 1632–48), who sought to bring together the Polish Vasa and the Habsburgs in an alliance that would support his aspirations to the Swedish crown and the desire of the Habsburgs to drive Dutch shipping out of the Baltic.

The second part analyzes the coming apart of the Vasa–Habsburg alliance under the reign of Wladislaw IV's successor, King John Casimir (r. 1648–68). This denouement is seen by Conde Pazos as the result of the weakness of King John Casimir and the inability of the Habsburgs to support him in his conflicts with Sweden and Prussia. In part, the failures of the Madrid Habsburgs to support the Polish king were due to their long war with France after the end of the Thirty Years’ War in 1648; and the failure of the Vienna Habsburgs to support him were due to restrictions to which they had agreed at the 1648 Treaty of Westphalia that ended that conflict. After repeated failures by Vienna to support Poland in conflicts with Sweden and Prussia, King John Casimir welcomed an alliance with France. King John Casimir, the last of the Polish Vasa, died in 1668, the same year the Habsburg emperor Leopold I signed a treaty with the king of France stipulating the division among themselves of the domains of their brother-in-law, King Charles II of Spain.

Conde Pazos's thorough analysis of the Habsburg alliance with the Polish Vasa is most valuable to Spanish language historians, but it is also valuable to historians of Poland and of Europe in general because of its insightful analysis of the role played by the Spanish Habsburgs in Northern Europe during the seventeenth century. Spanish archival sources, particularly from the Archivo General de Simancas in Valladolid, Archivo General in Madrid, and Archivo Histórico Nacional in Toledo, document many of his insightful comments on Spanish foreign relations with Poland during that century. The book also sheds light on the relations between the two branches of the House of Habsburg between 1632 and 1668 and on the economic and strategic reasons for their falling out in 1668, coinciding with the dissolution of their alliance with the Polish Vasa.