The following year the Norsemen suffered a series of decisive setbacks. Máel Sechnaill defeated them at Forrach (Farrow near Mullingar in County Westmeath). Tomrair (Þórir), the heir-designate of the King of Laithlind, was slain in a battle with Ólchobar mac Cináeda the King of Munster and Lorcán mac Cellaig the King of Leinster at Sciath Nechtain (near Castledermot in County Kildare). In the same year Tigernach mac Fócartai King of Loch Gabhair (Lagore, the royal seat of South Brega) inflicted a significant defeat on the Norsemen in an oakwood at Dísert Do-Chonna. These defeats culminated in an attack on Dublin itself in 849. The Viking settlement was plundered and probably destroyed – at least temporarily – by Máel Sechnaill, who was now High King of Ireland, and Tigernach mac Fócartai. A fleet of 140 longships arrived in Dublin in the same year. The expedition was led by "adherents of the king of the foreigners" and their objective was "to exact obedience from the foreigners who were in Ireland before them". It was also recorded that "afterwards they caused confusion in the whole country". It is possible that this fleet was sent by the King of Laithlind in an attempt to regain lost ground – or was he perhaps hoping to profit from the discomfiture of rival Scandinavians? The following year, we are told, the Norsemen formed an alliance with Cináed mac Conaing, the King of Cianachta North Brega, and plundered the territories of Máel Sechnaill and Tigernach and destroyed Tigernach's crannóg in Lagore. If this attack was in retaliation for the sacking of Dublin the previous year, it suggests that the fleet of 849 was indeed sent by the King of Laithlind. In 851 a significant development took place: "The Dubgenti came to Áth Cliath, made a great slaughter of the Findgaill, and plundered the naval encampment, both people and property." It is believed that this refers to the first appearance in Ireland of a new faction of Vikings. Called the "Dubgaill" or "Dubgenti" ("Dark Foreigners" or "Dark Gentiles"), these were possibly Scandinavians of Danish or Anglo-Danish origin who hoped to take advantage of the shifting fortunes of the town's inhabitants, known as the Findgaill or Findgenti ("Fair Foreigners" or "Fair Gentiles"), who were possibly Scandinavians of Norwegian origin – though there is still no consensus among historians as to the meaning of these terms.