Prior to finishing his education, the Neuendettelsau Missionary Society sent him to the Bethesda mission, near Hahndorf, in South Australia, where he joined an Old Lutheran community.

Johann Flierl was born in rural Germany, in Buchhof, a tiny farmstead (with three houses), near Fürnied, in the vicinity of Sulzbach, in the Oberpfalz, Kingdom of Bavaria.

At age thirteen, when he finished his studies at the local primary school, his father apprenticed him to a blacksmith, but changed his mind when he discovered that his son would have to work on Sundays.

Because Flierl had hoped since his early youth to serve as a missionary to the North American Indians, his father tried to send him to the seminary in Neuendettelsau, but was told his son needed to be 17 years old before he could enroll in the program.

[4] Bible Translators Theologians Flierl spent his first seven years of missionary life working on Lutheran Killalpaninna Mission (Bethesda) Station at Cooper Creek (1878–1885).

On his journey there, he was delayed for more than a year in Cooktown, Cape Bedford, North Queensland; the German New Guinea Company refused him passage.

[9] Despite his childhood and youth in a "unionist" parish (and one in which Catholics and all Protestants shared ecclesiastical facilities), Flierl came to mission work in New Guinea with a similar mind-set to Löhe's, formed by his education at Neuendettelsau seminary and his experience among the so-called Old Lutherans in southern Australia.

Another German missionary, Georg Bamler, joined them in 1887; the three men struggled with deadly diseases, primarily dysentery and malaria with its associated complications, and their discouragingly slow progress with the Kâte people.

[12] In 1889–1891, a particularly bad malaria epidemic wiped out almost half the European population on the coast; even Finschhafen itself was largely abandoned when the German New Guinea Company moved its operations to Stephensort (now Madang).

[13] Louise Flierl arrived later in 1889, but told her husband she would not stay unless he found a healthier place to live than the mosquito-infested delta lands around Simbang; upon further exploration, he identified a promising site at 700 metres (2,297 ft) in the highlands.

The local communities, though, were curious and frequently ascribed the presence of the missionaries to returning ancestors, benevolent spirit powers bearing material goods, and called them the Miti.

[15] To the Kâte, these men were different from the land-hungry planters, who rarely left the confines of their plantations; missionaries, on the other hand, were friendly, willing to explore the interior, and interested in knowing the people, their language, and their countryside.

[20] Flierl petitioned the synod in Australia frequently for new missionaries, and in 1899, it sent Christian Keyser, who, it turned out, offered the spark needed for the great breakthrough in 1905.

[21] Recognizing that his own usefulness in the Sattelberg had ended, in 1904, Flierl handed the directorship to Keyser, and moved himself and his family—which now included four children—to Heldsbach, 5.8 kilometres (4 mi) away on the coast.

The two missionaries running the Neuendettelsau station on the Sattelberg, Otto Thiele and Christian Keysser, seemingly turned a blind eye to the presence of the pesky Hermann Detzner, a regular army officer stranded on a survey mission in the interior at the outbreak of war; Detzner refused to surrender to Australian authorities and spent the duration of the war annoying the Australians by marching from village to village in the jungle, flying the imperial flag, and singing patriotic songs.

[25] During the war, Flierl also relied more on the connection between Lutheran churchmen in Australia and the United States, which he had nurtured carefully throughout the pre-war years.

[26] These new relationships were particularly important to maintain streams of personnel and supplies and became even more critical during the difficult post-war diplomatic and political dynamic of the Versailles Treaty negotiations.

[27] Flierl's youngest son, Hans (or Johann), went to Germany in 1914 to attend the Neuendettelsau Seminary in Franconia, and instead was conscripted into the German army; after the war, he also went to Texas, and eventually returned to New Guinea.