The struggle between New Sweden and New Netherland over control of the Delaware reached a critical phase when Dutch director general Petrus Stuyvesant made a voyage there in July 1651 and selected a location for a new Dutch fort, which was to replace Fort Nassau and Fort Beversreede. Stuyvesant first purchased all the land south of Fort Christina down to Bombay Hook (Boomtjes hoeck) from the Native Americans and ensured that the transaction was agreed upon in a format agreeable to European law. Then he selected “a reasonably suitable place [..] about a mile from the Swedish Fort Christina” to build a “fortress named Casimier,” which was furnished with “people and ammunitions of war, according to circumstances.” It has been suggested that he named the fort after Count Ernst Casimir van Nassau-Dietz, stadholder of Friesland from 1620-1632, but there is no direct documentary evidence to support this suggestion. During the First Anglo-Dutch which had broken out in 1652, the Swedes decided to try and conquer Fort Casimir. Swedish commander Johan Risingh, immediately upon his arrival on the Delaware River at the end of May 1654, sailed a ship up to the fort and sent out a sloop with twenty to thirty armed soldiers. As there was no gunpowder in the fort, the Dutch commander, sergeant Gerrit Bicker, decided to hand it over. He awaited the Swedish soldiers outside the fort, “in front of the gate,” which had been left open. Next Bicker, without giving any orders to his men, accompanied the Swedes into the fort where they easily overpowered the garrison of ten or twelve soldiers. Fort Casimir was renamed Fort Trefaldigheten (Fort Trinity), after Trinity Sunday, which in 1654 was May 31, the day it was captured. The Amsterdam directors were outraged by the behaviour of Gerrit Bicker, and called for his arrest. They also resolved to drive the Swedes from the river. For this purpose, they hired the warship Waeg which sailed for New Amsterdam at the end of May 1655. In the meantime, Swedish governor Johan Risingh had proceeded to strengthen Fort Trinity, by improving the walls and moving some cannon from his ship to the fort. These efforts, however, would prove of little avail. The Dutch expedition that sailed from New Amsterdam in 1655 consisted of four yachts, a galliot, a flute, and the warship Waegh, which had 36 guns. The smaller ships had about four guns each. The ships carried some 300 soldiers. New Sweden was quickly conquered. Stuyvesant appointed Jan Paul Jacquet as the new commander of Fort Casimir. Soon after his appointment, however, the West India Company directors in Amsterdam decided to transfer part of their possessions on the Delaware to the city of Amsterdam, in order to found a patroonship there under the name of New Amstel. Upon his arrival on 25 May 1657 Jacob Alrichs, vice-director of New Amstel, took formal possession of the fort, which, as he would soon complain, was in poor condition at the time. Alrichs found himself unable to repair the fort and improve other buildings according to his wishes, due to lack of building materials and provisions and the frequent outbreak of disease. After Alrichs himself succumbed to illness, command of the city colony passed on to Alexander d’Hinojossa, who took little care of the fortifications. The fort was in a bad condition when the English arrived in late 1664. Even so, d’Hinojossa and his troops refused to surrender. Thereupon Sir Robert Carr ordered a company of foot to land. Although the Dutch fired upon the soldiers, they managed to take the fort without losing a single man, killing three Dutch soldiers and wounding thirteen.