Johan (or John) Ernst of Nassau-Siegen or Hans Ernst (Dillenburg, 21 October 1582 - Udine, September 27, 1617) was a general in the Uskok War.
Johan Ernst was the eldest son of John VII of Nassau-Siegen and his first wife, Magdalena of Waldeck. Through his uncle, William Louis of Nassau-Dillenburg, he could join the Dutch States Army. He managed to stand out in the army of the States, so he became the commander of the "Oude Walen"-regiment and he was appointed as second in command during the War of the Jülich succession.
However, his ambitions were halted after the signing of the Twelve Years' Truce, and the Treaty of Xanten, which ended the warfare in the region.
In 1616 the Venetian Republic declared war on the Archduke of Styria, of Inner Austria. Early on, Venice addressed the Netherlands for support, whether in money, troops or ships, as the transportation of goods across the Alps to Venice was denied for years. Jan Ernst served in late September 1616 when the resident Suriano and got a contract for six months. The preparations lasted a month, but the Amsterdam shipowners argued excessive demands on the rental of twelve ships, so Jan Ernst emigrated to Enkhuizen and Rotterdam. Half way through November all ships were ready, but partly because of the unfavorable winds and storms, the ships were unable to leave for three months.
Meanwhile, mutiny broke out on the ships in Schiedam. Johan Ernst had serious problems with paying an advance on the pay as from the date of appointment and not from the date of exit. The inhabitants of Texel demanded money for all sailors who were housed by the island population. Johan Ernst lost his courage, because the Venetians would only pay when the soldiers arrived.
The captains had stashed food reserves for a period of three months and after a short period of time the sailors had already consumed 2,5 months supplies. The owners of the ships were increasing claims on Johan Ernst. It seemed that they would not get the profits which they had reckoned with, and they threatened to leave. The terrible boredom and frightening rumor that the Republic of Venice was about to negotiate peace, but also illness, expensiveness, mutual fights (and religious strife) played a disastrous role in that year. Only on March 2, 1617 the troops left the Texel, a ship stranded off the coast, the rest came on April 4 in the lagoon of Venice. Johan Ernst was granted the rank and title of General by the Doge of Venice, Giovanni Bembo.