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Thank you for your recent inquiry. In response to the first part of your inquiry, you may find the answer by reviewing the National Archives webpage on Naturalization records, available at https://www.archives.gov/research/naturalization/naturalization.html. As you will note on the webpage, naturalization of aliens dates back to 1790.
Regarding your second question, historically, service members were able to apply for citizenship based on their service to the United States military. From the webpage noted above, “Over 192,000 aliens were naturalized between May 9, 1918, and June 30, 1919, under an act of May 9, 1918, that allowed aliens serving in the U.S. armed forces during "the present war" to file a petition for naturalization without making a declaration of intent or proving 5 years' residence.“ For additional information you may find the webpage from the United States Customs and Immigration Service useful in locating the information you seek. The USCIS webpage on Naturalization through Military Service is available at https://www.uscis.gov/news/fact-sheets/naturalization-through-military-service-fact-sheet.
Thank you for your inquiry to the National Archives and Records Administration.