Pieter Krueler lived a remarkable life. The second son of a Transvaal Boer patriarch, his life was transformed when the South African War erupted in October 1899. Although he was only fourteen-years-old and was rejected by the local commando because of his age, he managed to find others that would take him. He served as a messenger carrying important warnings about Lord Methuen's march to relieve Kimberley; he took part in the battles at Colenso, Tugela, and Spion Kop; and, he was at Paardeburg when Piet Cronjé surrendered to the British in February 1900. The British marched the captured men, women, and children to a refugee (concentration) camp outside of Bloemfontein and there Pieter Krueler celebrated his next two birthdays while watching many succumb to the meager rations, lack of shelter, and poor medical care. After escaping with a friend from a burial detail in which he had to dig himself out of a grave, Krueler participated in commando service for the rest of the war.

After the South African War, most Boers (Afrikaners) who took up arms returned to their families and what was left of their farms, and attempted to rebuild their lives. Krueler could not settle down; his family was lost and his land was destroyed. He tried school, worked as a rancher, and, acted as a camp guard and later a dynamite expert for De Beers. The outbreak of war in 1914 once again gave him the sense of adventure he craved. Unlike most South Africans who loyally served under the new Union flag during the First World War, Krueler took up service with the Germans, first in South West Africa (Namibia) and afterwards, for most of the war, in East Africa (Tanzania). He trained and commanded locally recruited African troops. Krueler fought British soldiers at the Battle of Tanga with Paul Lettow-Vorbeck's forces, raided Belgian communications across the border, and even faced off against Jan Smuts and his South African and Rhodesian force.

What he did after the war remains unknown, but after a return to the mining industry and continued restlessness, Krueler headed to Spain in 1936. He went to make money as a mercenary, not concerning himself too much for the politics of the civil war. He recounts that he hated communists and fascists alike, but chose to join Franco's Nationalists after talking to a bunch of German pilots with whom he had much in common. Ultimately, however, he switched sides, joining the Basque cause and working hard to get Franco to offer the fiercely independent people neutrality. When those attempts failed, Krueler resigned himself to the Republican struggle, seeing it as the lesser of two evils. He trained men and ran mounted and foot patrols throughout the Basques region. Later he helped foreign volunteers escape to France through the Pyrenees, the same route he himself followed in 1938.

Returning to South Africa and to yet another war in 1939, Krueler was recruited by Smuts, then Prime Minister, to help train South African troops. Although he did not see combat during the Second World War, Krueler would have one more go in 1960, when at the age of 75, he was approached by De Beers to help with mining security issues. In the midst of a newly independent Congo spiraling into political chaos, Krueler became the de facto commander of more than 5,000 Black Congolese Katangan separatists fighting for Moise Tshombe. He remained in the Congo until the end of 1964. In the early 70s, Krueler's long and turbulent military and mercenary career came to an end after helping to train ‘anti-terrorist’ forces in Rhodesia. Although he was much too old to participate in any active missions, he helped instruct new recruits who were being to sent to eliminate the resistance of the Black nationalist forces taking part in the Chimurenga.

Although the authors of Four-War Boer, Colin D. Heaton and Anne-Marie Lewis, present some background and context to the various wars in which Krueler participated and cite a few secondary sources, especially in later chapters they rely mostly for their information on a series of interviews they conducted with Piet Krueler. Unfortunately, most of Krueler's claims are not substantiated in the text or in the notes. The authors also supply little analysis of Krueler's political choices and do not attempt to make any moral judgments about his actions. Sadly for the reader, neither does Krueler. Little introspection is offered in these pages – just a narrative of events. Readers will certainly enjoy some of the anecdotes, but they will learn little about these conflicts or about Pieter Krueler and why he acted the way he did.