former teacher Sir Simon de Burley was an insult not easily forgotten. With national stability secured, Richard began negotiating a permanent peace with France. A proposal put forward in 1393 would have greatly expanded the territory of Aquitaine possessed by the English Crown. However, the plan failed because it included a requirement that the English king pay homage to the King of Francea condition that proved unacceptable to the English public. Instead, in 1396, a truce was agreed to, which was to last 28 years. As part of the truce, Richard agreed to marry Isabella of Valois, daughter of Charles VI of France, when she came of age. There were some misgivings about the betrothal, in particular because the princess was then only six years old, and thus would not be able to produce an heir to the throne of England for many years. Although Richard sought peace with France, he took a different approach to the situation in Ireland. The English lordships in Ireland were in danger of being overrun by the Gaelic Irish kingdoms, and the Anglo-Irish lords were pleading for the king to intervene. In the autumn of 1394, Richard left for Ireland, where he remained until May 1395. His army of more than 8,000 men was the largest force brought to the island during the late Middle Ages. The invasion was a success, and a number of Irish chieftains submitted to English overlordship. It was one of the most successful achievements of Richard's reign, and strengthened his support at home, although the consolidation of the English position in Ireland proved to be short-lived. Second crisis of 1397–1399 The period that historians refer to as the "tyranny" of Richard II began towards the end of the 1390s. The king had Gloucester, Arundel and Warwick arrested in July 1397. The timing of these arrests and Richard's motivation are not entirely clear. Although one chronicle suggested that a plot was being planned against the king, there is no evidence that this was the case. It is more likely that Richard had simply come to feel strong enough to safely retaliate against these three men for their role in events of 1386–1388 and eliminate them as threats to his power. Arundel was the first of the three to be brought to trial, at the parliament of September 1397. After a heated quarrel with the king, he was condemned and executed.