The Regreg war was incited by Bhre Wirabhumi. The real name of Bhre Wirabhumi is unknown. His name simply means
Bhre (
Duke) of Wirabhumi, a province of Majapahit that corresponds with
the Blambangan area in the "eastern hook" of Java. According to Pararaton, he is the son of Hayam Wuruk with a concubine and adopted as a foster son by Bhre Daha (Rajadewi), the wife of Wijayarajasa. Later Bhre Wirabhumi would be married to Bhre Lasem sang Alemu, the daughter of Bhre Pajang (Hayam Wuruk's sister). According to
Nagarakretagama, the wife of Bhre Wirabhumi is Nagarawardhani, the daughter of Bhre Lasem also known as Indudewi. Indudewi is the daughter of Rajadewi and Wijayarajasa. The
Nagarakretagama is more valid than Pararaton since it was written during Bhre Wirabhumi's lifetime. During the reign of Hayam Wuruk and Wijayarajasa, the relations between the western court of Majapahit and the eastern court are described as somewhat an uneasy coexistence and mutual respect, since Wijayarajasa was Hayam Wuruk's father-in-law. After the death of Hayam Wuruk in 1389, he was succeeded by his nephew and also son-in-law,
Wikramawardhana. In the eastern court, after the death of Wijayarajasa in 1398, he was succeeded by his foster son that also his granddaughter's husband, Bhre Wirabhumi. Wirabhumi would rule the
Blambangan kingdom with
Lumajang as his capital. After the death of Indudewi, the position of Bhre Lasem was awarded to her daughter, Nagarawardhani. However, Wikramawardhana also bestowed the title of Bhre lasem to his wife, the queen
Kusumawardhani. That is why in Pararaton there are two Bhre Lasem,
Bhre Lasem Sang Halemu (The Fat Bhre Lasem) Bhre Wirabhumi's wife, and
Bhre Lasem Sang Ahayu (The Beautiful Bhre Lasem) Wikramawardhana's wife. The contest for the Bhre Lasem title has created an animosity between eastern and western courts, until 1400 when both Nagarawardhani and Kusumawardhani died. Wikramawardhana immediately appointed his daughter-in-law as the new Bhre Lasem, the wife of Bhre Tumapel. == Regreg war ==