Even before arriving at Sutter's Fort, the emigrants were met by a recruiting agent of the United States Army. Urged on by a companion to whom he owed money, Lienhard too signed up for a three months' service in the American military then engaged in war against Mexico in order to annex all its claimed possessions north of the Rio Grande. On the trek to Monterey, however, Lienhard became severely ill and barely survived the ordeal. On his return from Monterey in February 1847, he entered the service of the Swiss John Augustus Sutter (1803–1880). For the next six months he tended Sutter's fruit and vegetable garden on the Yuba River, then served several months as his mayor-domo at the Fort, and briefly also as a supercargo on Sutter's wheat laden schooner traveling to San Francisco. In January 1848 gold was discovered at Coloma where Sutter's sawmill was being built. At that time Lienhard was planting and tending a new garden of fruit trees, vines, vegetables, and flowers near the Fort. He was to join the miners only in August and, like others, in partnership with Sutter.