Chess opening are so complex and theoretical that amateur players will have trouble understanding them. An example is the Perenyi Attack of the Sicilian Defense (see diagram) which yields an immensely complicated and tactical position that even strong players have difficulty handling, and that is beyond the comprehension of most amateurs. Major changes in the rules of chess in the late fifteenth century increased the speed of the game, consequently emphasizing the importance of opening study. Thus, early chess books, such as the 1497 text of Luis Ramirez de Lucena, present opening analysis, as does Pedro Damiano (1512), and Ruy López de
Ruy González de Clavijo Ruy González de Clavijo Ruy González de Clavijo (died 2 April 1412) was a Castilian traveller and writer. In 1403-05 Clavijo was the ambassador of Henry III of Castile to the court of Timur, founder and ruler of the Timurid Empire. A diary of the journey, perhaps based on detailed notes kept while traveling, was later published in Spanish in 1582 ("Embajada a Tamorlán") and in English in 1859 ("Narrative of the Embassy of Ruy Gonzalez de Clavijo to the Court of Timour at Samarcand AD 1403-6"). Clavijo, a nobleman of Madrid and chamberlain to the king, set sail from