The German Side of the Story
The majority (95 percent) of those who settled in the Volga German colonies were refugees from the war-ravaged German states where religious strife and economic hardship had created a climate ripe for immigration. The bulk of those Germans came from Hesse and the Palatinate. Among other things, Catherine's manifesto promised religious freedom, exemption from military service, and thirty years without having to pay taxes.
For two centuries, a bloody battle was waged between the religious factions of Central Europe. By the end of the 30 Years' War in 1648, the Holy Roman Empire had disolved into more than 300 territories and independent cities led by secular or clerical rulers. These groups continued to battle on and off into the next century with opposing coalitions led by Catholic Austria and Protestant Prussia. The Seven Years' War began in 1754 and involved all the major powers in Europe at the time. The average inhabitant of Central Europe, regardless of religious or political allegiance, was under extreme tax burden, constant threat of injury to person or property, and routine conscription into military service for one side or the other. For many, there was little cause to remain.
The Russian Side of the Story
Only twenty-one days after her coronation in 1762, Catherine the Great issued a directive to her government authorizing them to admit into the country all persons who wanted to settle in Russia. A manifesto to this effect was issued on 4 December 1762. She wanted permanent settlers to populate the lower Volga frontier and bring stability to this region.
For centuries, the nomadic Kirghiz and Kalmyks had been ravaging the steppe of the lower Volga River basin. Russians and Ukrainians had attempted to settle there, but three battalions of soldiers sent to protect them had been slaughtered. In 1732, Empress Anna had turned to forced settlement of the area and sent Russian, Ukrainian, and Don Cossack settlers numbering 1,057 families to build a new defense line along the Volga between Tsaritsyn and Kamyshin. However, these settlers failed to defend the locale, but rather participated in robbery and murder along side the bandits.
Having observed the successful recruitment of over 300,000 Central European immigrants to Holland, England, Prussia, Austria, and even America, Empress Elizabeth in 1759 invited Austrians to settle in Russia. Catherine followed her example, but the 1762 manifesto had been worded in generalities and received a disappointing response. Catherine learned quickly why these early efforts were unsuccessful and, undaunted, she issued a second manifesto on 22 July 1763 that provided more specifics about who was covering transportation and settlement expenses and outlining protections and rights afforded to those who answered her call. More than 30,000 did so.
The above recount is much abbreviated. Each family undoubtedly had its own reasons for leaving. Each Russian official involved in the recruiting, transport, or settlement of the colonists had their own reasons for being involved in this enterprise. The following resources offer additional insight into these issues.
Beratz, Gottieb. The German colonies on the Lower Volga, their origin and early development: a memorial for the 150th anniversary of the arrival of the first German settlers on the Volga, 29 June 1764. Translated by Adam Giesinger. Lincoln, NE: American Historical Society of Germans from Russia, 1991.