of Belaya under Mikołaj Abramowicz (who in 1640 became the first Lithuanian General of Artillery). It is possible that in 1644 he took part in the Battle of Ochmatów. He spent some time in the Netherlands, where he was sent by the King Władysław IV Vasa to serve in the army of Duke Frederick Henry of Orange during the war with Spain; he participated in the Siege of Hulst in 1645. In 1646 he returned to Poland when Władysław created the Polish artillery corps and gathered specialists from Europe, planning a war with Ottoman Empire. He served as an engineering expert in the fields of artillery and rocketry in the royal artillery forces. From 1648 he served as Second in Command of the Polish Royal Artillery. In late 1648 the newly elected king John II Casimir Vasa, who had no plans for the war with Ottomans, advised him to return to the Netherlands and publish his studies there. There are rumors that in 1649 Siemienowicz became embroiled in a conflict with General of the Artillery Krzysztof Arciszewski over a bureaucratic matter; around 1649 he decided to leave the Commonwealth and work on his book in Amsterdam. Stance on poison gas Siemienowicz considered the use of poison gases dishonorable. In his work, he wrote:<blockquote>"and most of all, they shall not construct any poisoned globes, nor other sorts of pyrobolic inventions, in which he shall introduce no poison whatsoever, besides which, they shall never employ them for the ruin and destruction of men, because the first inventors of our art thought such actions as unjust among themselves as unworthy of a man of heart and a real soldier.</blockquote> Use of biowarfare In a historically early instance of biowarfare, Siemienowicz sponsored the firing of artillery containing the saliva of rabid dogs during a 1650 battle. While the success of this experiment is unknown, it demonstrated an educated guess about the disease's communicability that was not confirmed until the 18th century. It was popular in ancient warfare to catapult a deadly disease by using an infected cadaver or its parts to the enemy. One of the most notable examples was Genghis Khan's war against besieged Chinese cities, where he catapulted dead bodies infected with plague into cities. Artis Magnae Artilleriae In 1650 Siemienowicz published a notable work, Artis Magnae Artilleriae pars prima (Great Art of Artillery, the First Part). Its name implies a second