The opening of the border into Texas from the United States started before Mexican Independence. Moses Austin had been negotiating with Spanish authorities to allow him to bring families to populate the Area. It all was interrupted during the Independence movement. Later it was picked up by his son Stephen Austin, who successfully brought the first American families into Texas. Mexico indeed wanted a buffer between its bigger settlements and the Comanche. During Mexico's independence movement, Spain had to divert money and resources from the settlements and missions in its northern frontier. And after ten years of fighting, and independent Mexico was in no position to protect the area either. The Comanche raided as far south as the present states of Chihuahua, Sonora, Coahuila, Nuevo Leon, Tamaulipas, Zacatecas and San Luis Potosi. After Texas independence, Comanche raiders reached the city of Queretaro, about miles north of Mexico City. Chapter 5 of David Webber's "The Mexican Frontier deals with the subject. Personally, I do not believe it was a "misguided scheme" as Gwynne writes. It was a well thought of affair that was done in good faith. All Immigrants were to become Mexican Citizens, obey the local Laws, and convert to Roman Catholicism. Around 1834-35 the Mexican Government stopped allowing immigrants to com in, and tried to relocate Mexican Families into the area. This didn't stop the flow of immigrants who started to cross illegally and took possession of lands without any regard to the law. Further reading that might interest you is "The Alamo Story" by J. R. Edmondson, Chapters five and six deal with people who forced their way into Texas. The digital collection of the Texas State Library and Archives, you may find material that's close to primary sources, as well as the special collection (digital) of the Institute of Texan Cultures.