Here is a brief description of how Koxinga recovered Taiwan in an 1849 article " 海外異傳" written by 齋藤正謙 (1797-1865), a Japanese sinologist (漢學家):
"寬文元年（明永曆十五年、清順治十八年）[i.e., 1661]，成功自金陵喪敗，地蹙軍孤；永曆蒙塵南裔，聲問不通、存亡難詳，然猶奉正朔，將遷地謀恢復。適有紅毛通事 [Note: 何斌] [Note: 通事 was an official Dutch position responsible for communicating with and taxation of the Aborigines]，南安人也，與臺灣甲必丹歸一 [Note: Taiwan Captain = Coyett] 有隙，走廈門謂成功曰：『公何不取臺灣？公家之故土也。臺地沃野千里，為四省要害，橫絕大海，實霸王之區。紅毛蠢爾醜虜，因中國騷劇，竊占據之；破而取之易易耳』。成功大喜。
In 1661, Koxinga, having just been defeated in Nanjing, was in a precarious position. He had lost much territory and manpower and also lost contact with Emperor Yong-Li. The latter had escaped to Burma but it was unknown whether he was alive or dead. It was most urgent for Koxinga to re-group to continue his mission of restoring the Ming Court. Coincidentally at that time, a interpreter-representative working for the Dutch [by the name of He Bing who happened to be from Nan-An, Koxinga's hometown, and also held a grievous grudge against Governor General Coyett], advised Koxinga then in Amoy that "Why not take Taiwan, a land of your father's? Taiwan has thousands of acres of fertile fields. It is strategically located in an area of the sea that controls the access to the four provinces. It is certainly a land to re-build your power. The red-haired [i.e., the Dutch] are ugly and stupid. They were able to stealthily occupy Taiwan only because of the turmoils in China. They are in fact quite easy to defeat." Koxinga was very pleased with the advice.
"三月，親率兵三千二百人，揚帆至鹿耳門。門水淺沙膠，海舶至此，必易舟而入，故險易守。此時水適漲丈餘，成功得便戰艦銜尾而進。紅夷大驚，以為自天而下。成功引兵登陸，攻赤嵌城。城亂石疊，高數丈、厚丈餘，用土煆之，化為石灰。以砲擊城，城堅不受砲。城中紅夷千餘人，驅臺民數千，入而同守，且徵援兵於咬琉吧 [note: Batavia]。咬琉吧將領謀謂：『擣廈門之虛，則臺灣之圍自解矣』；乃率兵攻廈門。廈門留守洪旭迎擊走之。城久之不拔，臺民或告成功曰：『城外高山有水流于城濠，貫城而過。城中無井泉，所飲唯此一水；若塞其水源，三日而告變矣』。從之。紅毛勢窮，以巨艦十餘只決戰。
In the third month, Koxinga personally led 3,200 men and sailed to 鹿耳門, gateway to Zeelandia, where the water was shallow. Normally, all ships must cast anchors here and the transportation shifted to smaller boats. This of course favored the defenders. Koxinga's fleet, however, surprised the Dutch by riding the high tide with the ships in single file in queue to enter the bay and started a ground assault on Zeelandia. The fort was built of stones standing several meters tall with meter-thick walls. The walls were also reinforced with cement and were quite resistant to canon bombardment. Inside the fort, there were 1,000+ Dutch defenders who forced several thousand locals into the fort to help defend it. Coyett asked for help from Batavia. The generals there strategized that since the main Koxinga force had left Amoy which should be an easy target. And once Amoy was sacked, the siege of Zeelandia would automatically end. A fleet was quickly dispatched to attack Amoy. They were, however, beaten back by Amoy's defending army commanded by General Hong Xu. And at the same time, Koxinga heeded the counsel of the locals to cut off the sole water supply, a river that flowed through the fort. Coyett decided to counter-attack with 10+ huge warships.
Koxinga's soldiers entered the Dutch warships through the gun ports and took over five ships. The rest were all burned and destroyed and 600 Dutchmen were killed. With the redoubt of Zeelandia sacked, Coyett capitulated after Koxinga sent a messenger to tell him that "Taiwan was developed by my father. I am content to recover the land. You may take whatever your treasured items with you. I do not need them at all." The Dutch surrendered and were sent home:
From the Dutch side, a far more detailed account as part of a thesis on Dutch VOC, "The Shameful Fall of Fort Zeelandia" by Tristan Mostert (2009), can be found here. For example, an eyewitness looking out from Fort Zeelandia reported the following:
“In the morning of the 30th of April, as in the entire preceding night, there was a very thick mist, due to which one could not see into the distance. As soon as the mist had cleared, however, we saw such a fleet of ships, to wit Chinese junks, lie before the harbour in front of Baxemboy, that we could not oversee them, let alone count them. There were so many masts, that it looked like an arid forest. We looked at this, all of us equally awestruck and puzzled, as no-one, not even our Lord Governor, had expected anything like this, and we did not know, whether they were friend or foe.”
This was the arrival of 25,000 soldiers led by Koxinga on hundreds of war junks. And Lord Governor Coyett would soon find out what Koxinga's intention was.
The map below shows where Zeelandia and Provintia were located. Other landmarks are: Lakjemuyse Channel = 鹿耳門 [where Koxinga's fleet entered the bay]; Baxemboy = 北線尾 [where half of 240 musketeers including Captain Pedel were slain by Koxinga's Iron-man corps]; Tayouan = 大員 [or 台灣]; Tai Bay = 台灣; and Sakam = 赤崁社 [a Siraya Aboriginal 西拉雅原住民 Settlement].
[Note: this is re-posted from http://danshuihistory.blogspot.com]