Enrico Dandolo was the ruler of Venice, a wealthy Italian city-state, from 1192-1205. He is most commonly remembered for the Fourth Crusade and the Sack of Constantinople in 1204. The Sack of Constantinople was instrumental in the decline of the Byzantine Empire and eventually precipitated the Fall of Constantinople in 1453 and the rise of the Ottoman Empire in Europe.

John Wycliffe was a notable theologian and dissident within the Catholic Church in the fourteenth century. He is most famous for translating the bible into English for the first time. He is also considered to be a progenitor of the English Reformation for his rejection of church authority and his attacks on clerical indulgences.

All of these inventions occurred during this time period and dramatically improved agricultural production throughout Europe. The heavy plow was able to break up denser soil and broke much less frequently, allowing for greater agricultural efficiency. The horse collar and horseshoes turned horses into extremely efficient tools for agricultural production. The tidal mill allowed communities and farmers to use the power of tides and rivers to fuel water mills and provide energy. 

Prior to the invention of the cannon in the fourteenth century, the most useful weapon a lord or a king could have was a castle. Castles were built of stone and could withstand constant barrage from trebuchets and catapults provided they were sufficiently manned; however, the invention and subsequent improvement of the cannon gradually rendered castles obsolete as the additional firepower of a cannon could blast right through the stone walls of a castle. This changed not only military life, but also social, economic, and political life in Europe as the feudal system, predicated in many ways on the protection offered by the lord's castle or stronghold, became gradually obsolete.

The seed drill was not invented in Europe until the 1700s, centuries after the High Middle Ages ended. The High Middle Ages period (c. 1000-c. 1300) was partly characterized by warmer climates in Europe than in preceding or subsequent periods, and this helped encourage increased food production. Food production was also helped in this period by land reclamation, which expanded the areas of land being cultivated, as well as the collared harness (which allowed more efficient use of horses as draft animals), and improved plows (which better enabled cultivation in a wider variety of soils).

The "Vikings" were a Nordic seafaring race from Scandinavia who were influential in European history from roughly the seventh century to the twelfth century. They are most notable for the innovations in shipbuilding which allowed them to travel long distances, pillage coastal communities throughout Europe, and even reach as far as North America.

The kings of Europe, even those unconcerned with the "spiritual gains" to be made through the Crusades, were generally in support of them. That is because the Crusades offered no direct threat to their power and meant that many of the young, quarrelsome nobles, who would otherwise engage themselves in costly wars in Europe, were sent away. 

The Crusades negatively affected European society because they led directly to an increased persecution of the Jewish population of most European countries. The idea that young Christians should be dying in religious wars to liberate the Holy Land while the "enemies of Christ" continued to live among Christian societies was abhorrent to many, and pogroms and other massacres and persecutions of Jewish people increased in regularity.

The Third Crusade was waged from 1189 to 1192 and was an important part of the centuries-long attempt by Christian Europe to retake the Holy Land of Jerusalem from the Islamic Kingdoms. The Third Crusade was somewhat successful, although it failed in its main goal of retaking Jerusalem. It is sometimes called the "King's Crusade" because it was led by various kings of Europe, including Richard the Lionheart of England, Phillip II of France, Emperor Frederick Barbarossa of Germany, and Leopold V of Austria.

The Crusades led directly to all of these consequences except an increase in religious tolerance in Europe. Rather, the Crusades contributed to a growth of religious intolerance (particularly against Jewish people) in Medieval Europe. The Crusades led to a growth of the European middle class because so many landed nobles and aristocrats perished in the efforts to retake the Holy Land; they left a power vacuum that was filled by the middle class, which had grown wealthy from the increase in trade caused by the same endeavor. The authority of the church also increased as Christendom became somewhat united behind one goal. Finally, technological innovation was encouraged in Europe by the returning knights who brought with them ideas and mathematical theories developed in the Islamic world.