The expansion of the Swiss Confederation between the Battles of Sempach and Marignano (1515) caught the attention of the European powers. The military strength of the confederation was founded on a militia of young people that was difficult to lead and often practiced blackmail or ravage but that stuck together in danger and developed a successful model for fighting knights with lances. Politically, non-Habsburg emperors—especially Sigismund (1368–1437), the king of Hungary, Germany, Bohemia, and Lombard and the Holy Roman emperor—granted privileges to the confederates, confirming their status as imperial towns and free communities. Thus, “turning Swiss” became an option for those German entities that disliked princely and usually Habsburgian territorial rule. Without becoming full members of the confederation, rural areas such as Appenzell (1411), republican towns such as Sankt Gallen (1454), Schaffhausen (1454), Mulhouse in Alsace (1466), and Rottweil in Swabia (1463), princes of the church such as the abbots of Sankt Gallen (1451), and the two other confederations of rural communities, the Valais and the Graubünden, eventually adopted the status of Swiss allies (Zugewandte). These allies took part in several wars and were invited to the meetings of the Diet (Tagsatzung), but, unlike the regular members, they neither possessed a full vote nor shared in the administration of the joint dependencies (gemeine Herrschaften). These dependencies were governed alternately by those cantons that had conquered them. As even the regular members were connected by many separate bilateral or multilateral treaties with different rules, Switzerland was really only a network of alliances rather than a state until 1798.

Nevertheless, beginning in the 15th century, the confederation gradually became a power of order in the neighbouring area, even though it usually did not act as a whole, but only those cantons that were directly involved became politically active. Thus, it was mainly Schwyz that intervened in favour of Appenzell against the abbot of Sankt Gallen, while Uri followed its designs on territory south of the Alps. But, initially lacking the support of other cantons, it was prevented in the early 15th century from expanding into Italian-speaking Ticino by the viscount of Milan. In 1415, during the ecumenical Council of Constance, Sigismund invited the Swiss to weaken Frederick IV, the Habsburg supporter of an antipope, and conquer his ancestral territory, Aargau (Argovie), which had separated Zürich from Lucerne and Bern. Thus, Aargau became the confederation’s first joint dependency. From 1424 (until 1712) the Diet became regular and assembled in the Argovian town of Baden to discuss common affairs and especially the administration of joint dependencies.

Soon after, in the eastern part of present-day Switzerland, the ambitions of Zürich, which invited Austrian and French support, clashed with those of Schwyz, which found support with the other confederates. In the bitter Old Zürich War, which erupted in the late 1430s, Schwyz and its allies thwarted Zürich’s attempt to gather a territory under the protection of its legitimate Austrian overlord and brought the city back into the internal balance of powers within Switzerland. Peace was finally restored in 1450, when Zürich renounced the Austrian alliance and Schwyz gained control of territory on the southern shore of Lake Zürich. While Zürich’s expansionist aims thus were blocked in the south, it purchased suzerainty over the town of Winterthur in the east (1467). In 1460 Pope Pius II entitled the Swiss to conquer Thurgau, another Habsburg territory in the east, near Lake Constance, which as a result became a joint dependency.

With the conquest of Thurgau and especially as a result of the Burgundian War (1474–77), Switzerland became a dynamic European power for half a century. Charles the Bold, duke of Burgundy, had tried to establish an empire extending from the Netherlands to the Mediterranean and gradually gained control of pawned Austrian territory from Alsace to the Rhine towns of Rheinfelden and Waldshut. Along the upper Rhine, Strasbourg, Basel, and Mulhouse sought support against Burgundian pressure and found it in Bern, whose commercial routes toward the west and north seemed endangered. Backed by an unprecedented peace and alliance with the Habsburgs and by the machinations of France’s Louis XI, the confederates won a series of spectacular encounters, including those at Grandson, Murten, and Nancy (1476–77). Charles the Bold eventually was killed, which ended his attempt to resurrect the Lotharingian empire and benefited France and especially the Habsburg heritors of the Netherlands.

The victory over Burgundy strengthened the position of the cities within the Swiss Confederation that wanted to welcome their wartime allies Fribourg and Solothurn into the league. The proposed expansion provoked a major crisis between the rural and urban oligarchies, which already had clashed over the Burgundian booty and generally had different interests. The towns were oriented toward commerce and interested in a more effective subjection of the countryside, which led to peasant uprisings such as those against Hans Waldmann, the burgomaster and virtual dictator of Zürich in the 1480s. The rural cantons sympathized with these peasants and also tolerated undisciplined freebooting; furthermore, these rather poor areas became even more dependent than the urban elites on the revenue generated by the increasingly professionalized mercenary system that supplied Switzerland’s renowned troops to the princes of Europe.

Owing to the mediation of the hermit Nicholas of Flüe, the Diet of Stans (1481) agreement was reached, averting civil war by allowing Fribourg and Solothurn to join the Swiss Confederation, banning private war. The towns were required to renounce the separate alliance they had formed and to seek approval by the confederation for any future alliance that they might negotiate. This compact—the so-called Stanser Verkommnis (Contracts of Stans)—remained one of the very few treaties to include all of the cantons and was regularly renewed. Indeed, no common constitution existed prior to 1798.

In 1495 Holy Roman Emperor Maximilian I and the imperial Diet at Worms imposed a public peace and a Reichskammergericht (Imperial Chamber of Justice), which served as the empire’s supreme court. Like other peripheral regions, the Swiss Confederation opposed the intensification of the authority of the Habsburg ruler. Tensions also increased because of the antagonism between Swiss and Swabian mercenaries and a series of predatory excursions by both. The confederates were accused of being sacrilegious enemies of the nobility and true order. In 1499 Maximilian joined with the Swabian League, an alliance of southern German princes, knights, and cities organized to maintain public peace, and attacked the Swiss ally Graubünden, thus igniting the Swabian (or Swiss) War. After several battles in Graubünden and along the Rhine from Basel to the Vorarlberg, peace was declared at Basel on September 22, 1499; the Swiss Confederation did not adhere to the decisions of Worms, but it remained a subject of the empire even though there was little effective control left. Within two years the strategic Rhine territories of Basel and Schaffhausen joined the Swiss Confederation, and in 1513 Appenzell also became a full member.

Following the Swabian conflict, Switzerland was drawn into the struggle between the Holy Roman emperor, France, Spain, and the Italian powers over control of the duchy of Milan. The Swiss had more than a passing interest in this area, having followed Uri and extended their control into the southern Alpine valleys while fighting against the Milanese during the 15th century. The elites of the cantons were divided according to their contrasting foreign sympathies and the bribes they received for selling mercenary troops. At first the Swiss supported France, but later they joined the alliance led by the pope to drive the French out of Italy. In September 1515 a disunited Swiss force was decisively defeated on the fields of Marignano southeast of Milan, losing some 10,000 infantrymen in a battle against the French army, which used recently invented artillery and a modern cavalry.

The terms of the peace settlement of 1516 with French King Francis I were generous to the vanquished Swiss Confederation, which kept most of present-day Ticino as a joint dependency, while the Valtellina was accorded to the Graubünden. The goodwill generated by the peace terms and the mercenary pact of 1521 resulted in more than 250 years of accord between the former belligerents and had important economic consequences for Switzerland, giving confederate merchants access to the large French market. Although the traditional trade with the empire and Italian states continued, France became, in keeping with the general shift of commerce toward the Atlantic countries, the main market for Swiss products (principally textiles and cheese and later books, jewelry, and watches) until the French Revolution.

The defeat at Marignano marked the end of Switzerland’s role as a European power and eventually—but not intentionally—led to a politics of neutrality. Its political structure as a federation of independent states no longer could match the efficiency and resources of the growing united monarchies. In particular, a common and active foreign policy became impossible as the Reformation added another dimension to the heterogeneity of the confederation, already split because of different regional interests and especially the opposition of rural and urban cantons. Nevertheless, the Swiss Confederation had shown more signs of institutional consolidation and cultural similarity in the 15th century than it would in the three following centuries. By 1500 it had established a historiographical tradition and a sense of itself as a political entity based on its shared topography and history; moreover, foreigners regarded it as an entity.