of Cambodia, Chey Chettha II (the marriage seems to have been contracted years earlier). As a result of this marriage, the Cambodian King allowed the Nguyễn to establish a small trading and tax post at Prei Nokor what is now Saigon in 1623. Vice versa, Nguyễn clan have to supply the weapon and troops to support Cambodian war against Ayutthaya Kingdom. This settlement was the start of a major expansion by the Vietnamese beyond the borders established by Lê Thánh Tông in 1471. According to the Italian missionary Christoforo Borri who was staying in Quy Nhơn witness the military support of Nguyễn Phúc Nguyên sent to Cambodia, according to his records (published in 1631): Lord Nguyễn Phúc Nguyên sent his military support to his son-in-law Chey Chettha II twice to against Siamese. In 1623, the mission from Nguyễn was dispatched to Oudong, with a lot of treasures and gift to strengthen the relationship between two government and confirm the alliance of Cambodia and Nguyễn. After the negotiation, Chey Chettha II allowed to let them established the trading post which were namely Kas Krobei (Vũng Tàu) and Prei Nokor (Saigon) for taxation. Nguyễn lords can bring their private army to protect the post and their citizens as well as the public security of the city of Prei Nokor Trịnh–Nguyễn contention With the death of Trịnh Tùng in 1623 and the new rule of his son, Trịnh Tráng, another formal demand was made by the Court in Hanoi for the Nguyễn to pay tribute. In 1624, Nguyễn Phúc Nguyên formally refused. Three years later, the Royal (Trịnh) army marched south and attacked the Nguyễn. The first set of battles lasted for four months but the Nguyễn armies were not defeated and Phú Xuân was not taken. The Royal army withdrew north to regroup. The Nguyễn immediately began the building of a massive pair of walls to defend their lands. This pair of walls, just south of the Linh River, eventually grew to a length of 11 miles, stretching from the sea to the mountains. The walls were each 20 feet tall and equipped with many cannons of European design. In 1633, the Trịnh tried to outflank the walls with an amphibious invasion but the Nguyễn fleet was able to defeat the Royal (Trịnh) fleet at the battle of Nhat-Le. Death Nguyễn Phúc Nguyên died in 1635 with the war still going on.