He served the Republic of the United Netherlands in diplomatic missions, as an officer in the Dutch States Army, and as governor of Hulst.

Henry was born at Siegen Castle [de] on 9 August 1611[1][note 1] as the fourth son of Count John VII 'the Middle' of Nassau-Siegen and his second wife, Duchess Margaret of Schleswig-Holstein-Sonderburg.

[6] In the Eighty Years' War he distinguished himself at the Siege of Gennep [nl] in 1641 and in the Rijk van Nijmegen.

[9] At the court of Queen Christina of Sweden, Henry met his sister Amalia and her husband, field marshal Herman Wrangel af Salmis, governor of Livonia.

[1][6][10][11] The later scientist and inventor Christiaan Huygens, whose knowledge of the law in the Deensche saecke (Danish affairs) would be of use to Henry, accompanied him as a secretary.

John 'the Younger' had the imperial decree read out, and when his brothers demurred, he said as he stood up: "Der Kaiser wird uns scheiden!"

He had taken the precaution of obtaining a further imperial decree on 20 November 1623 against Countess Dowager Margaret and her sons, in which the Emperor strictly forbade impeding John's assumption of government, his taking possession of the land and his inauguration.

However, for a short period (1632–1635) this situation underwent a temporary change: during the Thirty Years' War, his brothers, who were fighting on the Protestant side, rebelled against John 'the Younger'.

[18] Count Louis Henry of Nassau-Dillenburg entered the service of King Gustavus II Adolphus of Sweden on 1 December 1631, who had landed in Germany on 24 June 1630 to intervene in favour of the Protestants in the Thirty Years' War.

[22] Countess Dowager Margaret, through the mediation of Louis Henry, turned to Gustavus Adolphus and asked for help against the machinations of her stepson John 'the Younger'.

On 14 February 1632 the Swedish king sent an order from Frankfurt to Louis Henry to provide military support for his first cousin John Maurice.

However, the latter soon restored the old order: in 1636, he again became the sole owner of his father's property, with the exception of Hilchenbach, which he left to William, and he again governed the city of Siegen alone.

[25] On 22 January 1645, after his return from Brazil, the latter, with his brothers George Frederick and Henry and an 80-man entourage, had forcibly occupied Siegen Castle and on 15 February had received the renewed homage from the citizens, albeit this time only for two thirds of the county.

Already before his departure to Brazil, on 25 October 1635, he had explicitly authorised his subjects to recognise the then still living John 'the Younger' as co-ruler.

[27] In 1645 John Maurice relinquished his rights to the Freudenberg district, granted by the will of 1621, in favour of his brother George Frederick.

[4][5][10] William Maurice, Sophie Amalie and Frederick Henry were elevated to the rank and title of prince(ss) in 1664.