999 - Sweyn Forkbeard prepared for war

Riding to battle
Tyre the sister of Sweyn Forkbeard married with Olaf Tryggvason, she did it without the permission of Sweyn Forkbeard, Tyre had previous been married to the chieftain of the Jomsvikings, Styrbjorn, but he died in a battle at Uppsala and before that she was married to a Vendic duke Boleslaw, which she left.

The marriage made Sweyn Forkbeard angry and stimulated further his wish to reconstruct the supremacy of Harald Bluetooth over Southern Norway. A number of alliances had strengthened the position of Sweyn Forkbeard, he sent his wife Gunhild home to her father Mieczylaw of Poland and instead he married the widow of the Swedish king Erik the victorious, Sigrid Storråde, who was mother to the Swedish king Olof Skotkonung.

The refugees and sons of Earl Haakon Svend and Erik had been married into the Swedish and Danish royal families by marrying Olof Skottkonnungs sister Holmfrid and the daughter of Sweyn Forkbeard named Gyda.
Danes ravaged Kent and sacked Rochester.
Faroe Islands
Sigmundur Brestisson (961 – 1005) returned from a Norwegian exile to introduce Christianity to the Faroe Islands.
10th century Viking warrior
Late in 999, the Leinstermen, allied with Dublin vikings and revolted against Brian Boru. This provided the opportunity for Sigtrygg' Silkbeards second alliance with Máel Mórda mac Murchada. Brian Boru's armed forces defeated  the Irish-Viking army on the 30th december at the Battle of Glenn mama, and followed the victory with an effective attack and conquest upon Dublin. Brian Boru pronounced himself as emperor of the Irish.
Widespread viking raids from Vikings in Ireland and Island of Man.
A group of Norman christian pilgrims returning home from Jerusalem stopped at Salerno. While they were staying there, the city was attacked by Saracen pirates. The people of Salerno were afraid to fight, but the warlike Normans were ready to fight. Soon their toughness drew out the Muslims.  
Guaimar III of Salerno offered the Normans money to stay, but they refused it. Before they left,  the Normans promised to spread the word about the need for defenders against Muslim raiders.

Ship building
Sweyn fork beard had previously attempted to attack Norway, he sent the mercenary corps the Jomsvikings against the rebellious Earl Haakon, but the Jomsvikings were defeated at battle of Hjørungavåg (Probably Hareidlandet, south of Alesund).
Leif Erikson was blown off course when traveling to the Hebrides , he arrived in Norway during summer and became a hirdman of King Olaf Tryggvason. He converted to Christianity and took up the mission to christen Greenland.
The Church of St. David at Menevia was destroyed and the Bishop Morgeneu was killed by Vikings.