Being in a forlorn hope was a dangerous enterprise as the name implies. They were created by amalgamating musketeers from various infantry units or using dismounted dragoons. The formation was more mobile than the traditional pike and shot but very vulnerable to horse.
The formation was used in a number of the early battles. At Wimpfen (May 1622), the Margrave of Baden detached his extra musketeers to fight as a forlorn hope. At Hoechst (June 1622), Tilly employed three forlorn hopes to screen his advancing tercios when these tercios advanced across the Sulzbach creek.
The Sulzbach creek, which is a prominent feature of the battle of Hoechst, is a stream that flows pretty close to the office where I work. Unfortunately most of the area has been developed in the last fifty years. The stream itself is only really active after snow melts and heavy rain showers. In the summer it is a trickle but has over the years carved out a small valley. It is on the west ridge that the Protestants placed their forces. The Imperial tercios advanced up the eight foot (3m) embankment to attack two redoubts near Sossenheim.
At Alte Veste (September 1632) the Swedes advancing against the earthworks found the woods too difficult for their pike and sent the musketeers forward as a forlorn hope. At Lutzen it could be argued that Henderson Dragoons acted as a forlorn hope in that they were on foot in the second line.
Protestant Forlorn Hope including a couple of Halberdiers identified by their blue sashes
Text: Battles of the Thirty Years War From White Mountain to Nordlingen, William P. Guthrie, Greenwood Press, 2002.