The Alemanni cross the frozen Rhine in large numbers, invading the Roman Empire.
The Rhine is one of the major European rivers. The river begins in the Swiss canton of Graubnden in the southeastern Swiss Alps, forms part of the Swiss-Liechtenstein, Swiss-Austrian, Swiss-German and then the Franco-German border, then flows in a mostly northerly direction through the German Rhineland and the Netherlands and eventually empties into the North Sea.
It is the second-longest river in Central and Western Europe (after the Danube), at about 1,230 km (760 mi), with an average discharge of about 2,900 m3/s (100,000 cu ft/s).
The Rhine and the Danube comprised much of the Roman Empire's northern inland boundary, and the Rhine has been a vital navigable waterway bringing trade and goods deep inland since those days.
The various castles and defenses built along it attest to its prominence as a waterway in the Holy Roman Empire.
Among the largest and most important cities on the Rhine are Cologne, Dsseldorf, Rotterdam, Strasbourg and Basel.
The Alemanni (also Alamanni; ) were a confederation of Germanic tribes on the Upper Rhine River. First mentioned by Cassius Dio in the context of the campaign of Caracalla of 213, the Alemanni captured the Agri Decumates in 260, and later expanded into present-day Alsace, and northern Switzerland, leading to the establishment of the Old High German language in those regions, by the eighth century named Alamannia.In 496, the Alemanni were conquered by Frankish leader Clovis and incorporated into his dominions. Mentioned as still pagan allies of the Christian Franks, the Alemanni were gradually Christianized during the seventh century. The Lex Alamannorum is a record of their customary law during this period. Until the eighth century, Frankish suzerainty over Alemannia was mostly nominal. After an uprising by Theudebald, Duke of Alamannia, though, Carloman executed the Alamannic nobility and installed Frankish dukes.
During the later and weaker years of the Carolingian Empire, the Alemannic counts became almost independent, and a struggle for supremacy took place between them and the Bishopric of Constance. The chief family in Alamannia was that of the counts of Raetia Curiensis, who were sometimes called margraves, and one of whom, Burchard II, established the Duchy of Swabia, which was recognized by Henry the Fowler in 919 and became a stem duchy of the Holy Roman Empire.
The area settled by the Alemanni corresponds roughly to the area where Alemannic German dialects remain spoken, including German Swabia and Baden, French Alsace, German-speaking Switzerland, Liechtenstein and Austrian Vorarlberg.
The French language name of Germany, Allemagne, is derived from their name, from Old French aleman(t), from French loaned into a number of other languages, including Middle English which commonly used the term Almains for Germans. Likewise, the Arabic name for Germany is ألمانيا (Almania), the Turkish is Almanya, the Spanish is Alemania, the Portuguese is Alemanha, Welsh is Yr Almaen and Persian is آلمان (Alman).