1. Will of Duke Gotthard. Mitau/Jelgava Castle, 7 December 1573. Parchment. LVVA, Collection 1100, Inventory 13, File 726.

During his life Duke Gotthard compiled at least three wills, which were intended to provide the legal basis for inheritance of the duke's throne. In this will Gotthard stipulated that after his death he was to be buried without ostentation in Goldingen/Kuldīga Church. The duke granted scholarships to six pupils from Latvian families, or pupils who knew Latvian from poor German families, to attend schools in Goldingen/Kuldīga, Mitau/Jelgava and Selburg/Sēlpils, with the intention of education them as pastors for Latvian congregations. Most interestingly, already in this will Gotthard stipulated that after his death two dukes (but no more) might rule the duchy, even though at that time the duke only had one son, Frederick. The other, William, was not yet born. The elder son would thus inherit Courland and part of Semigallia along with Mitau/ Jelgava, while the younger son would have the rest of Semigallia, including the centres of Selburg/Sēlpils and Bauske/Bauska. However, the duchy was not to be divided into two separate parts, and the fief was to be received jointly at the court of Poland-Lithuania. This will was witnessed in Mitau/Jelgava Castle in the presence of witnesses by notary Ieremias Miethe.

2. Letter from Zacharias Stopius to Duke Gotthard. [Riga, 1577]. LVVA, Collection 1100, Inventory 13, File 722, Vol. I.

Like other rulers of that time, Gotthard Kettler had an interest in astrology and various predictions about the future. In 1567 he hired the Riga city physician (doctor) Stopius, who practiced not only medicine, but also astronomy and astrology, the two still being closely connected at the time. Stopius is the author of the first calendar for Latvia (Schreibcalender auf das Jahr .. 1565), published in Königsberg in 1564, and the population centre of Stopiņi bears his name. In the letter Stopius states that he is sending the duke an astrological prediction compiled by a Lübeck physician and astrologist who used different methods than Stopius himself. In 1577 the appearance of a threatening comet was expected, regarded as a portent of great calamities, for which reason astrological predictions were seen as very important at the time.

3. Address with the name and title of Duke Gotthard. 1566. g. LVVA, Collection 554, Inventory 1, File 26, Volumes I–III.

Gotthard Kettler's new title was: Duke of Courland and Semigallia in Livonia (in Liefland zu Curland und Semgallen Herzog). Initially, Gotthard was also given the post of Governor of the polish Livland, but he lost this post in 1566, when, along with the establishment with the Trans-Daugava Duchy (Ducatus Ultradunensis), the king appointed Jan Chodkiewicz, Grand Marshal of Lithuania, as administrator of polish Livland.

4. Letter from Gotthard to an unknown official concerning payments and gifts in the court of Poland-Lithuania. C. 1572. LVVA, Collection 554, Inventory 3, File 180.

Since the Duchy of Courland was a fief of Poland-Lithuania, the duke needed approval for the most important documents from the king. Various conflicts between the duke and his subjects were also resolved in the Polish-Lithuanian court. It was impossible to obtain the favour of officials without bribes and gifts, which was an official practice at that time. In the document Gotthard lists the information provided by his secretary in Warsaw, Oswald Groll, regarding payments in the king's court. Thus, to obtain approval for his will, the duke had to pay 300 or 400 thalers, along with a fee of 200 thalers to the vice-chancellor, and a gift of a horse worth 600 guilders, along with some excellent dogs, to the King of Poland. Grand Chancellor and Marshal Radziwiłł received a good horse and Frederick Zalesky obtained a gold chain worth 100 thalers for his support.

5. Gotthard's last will. Mitau/Jelgava Castle, 23 February 1587. Parchment. LVVA, Collection 554, Inventory 1, File 39.

In this will, compiled a few months before he died, Duke Gotthard requested that he be buried in the vault of the newly established church in Mitau/Jelgava Castle. The duke set out specific instructions with regard to churches, schools and hospices in a separate appendix, which has, unfortunately, not survived. The duke bequeathed his authority to his two sons, Frederick and William, repeating the instruction that the unity of the duchy be maintained. Frederick was granted Semigallia, with the centre at Selburg/Sēlpils, whereas William was granted Courland, with the centre at Goldingen/Kuldīga. Frederick would receive Mitau/Jelgava after the death of his mother. Until William came of age, the court was to reside alternately in Goldingen/Kuldīga and Selburg/Sēlpils. Since the elder son, Frederick, was only 17 at the time, Gotthard also nominated 10 councillors who were to help the young duke in matters of administration, i.e. in essence he put together a government.

6. Promissory note of Duke Gotthard. Grünhof/Zaļenieki, 26 March 1579. LVVA, Collection 1100, Inventory 13, File 729.

Although the Livonian War had virtually no direct impact on The Territory of the Duchy, the duke and his subjects were obligated to provide both military and material assistance to the feudal overlord, who was waging war in Livland. Maintenance of the state apparatus, trips to see the king and various other expenses quickly emptied the duke's coffers. This meant that the duke was often forced to borrow money or purchase goods on credit. This is illustrated by a promissory note issued by Gotthard, in which the duke promises to pay back in money or in kind within 3 years the sum of 600 thalers to Thomas Cardinal, Captain of Windau/Ventspils.

7. Gotthard's instruction to his envoys in Warsaw, Georg von Tiesenhausen and Samuel von Wolpen. Mitau/Jelgava, 20 May 1587. LVVA, Collection 554, Inventory 1, File 26, Volume XV.

This document supplements an earlier instruction from the duke on the questions that the envoys were to pursue in Poland-Lithuania. However, the document is interesting not only because of its content. According to the generally accepted version, based on the repeatedly published Chronicle of Salomon Henning (1528–1589; chronicle first published in 1590 and 1594), the duke died on 17 May 1587, but this document, signed by Gotthard himself, is dated 20 May. We may ask how this is possible? Either the clerk has given an erroneous date (the instruction followed by the supplement, having been dated 12 May), or the date has been added later, or there was a printing error in the first publication of the chronicle, and the duke actually died later, for example, on 27 May. The announcements sent out by Duke Frederick to inform of the death of his father are of no help in resolving the matter, either, since they only give the date of the funeral: 2 July. How can this riddle be solved?