When Haydn completed his Opus 20 String Quartets in 1772 he was in his fortieth year and was on the brink of international fame. Since 1761 he had been in the service of the Esterházy family at their castle in Eisenstadt, east of Vienna, or, after the mid-1760s, mainly at the palace of Eszterháza, over the present-day border with Hungary on the other side of the Neusiedlersee.