Early Christian attitudes to warfare and military service have long been a subject for keen interest but not always without biases. Quite often the motivation for studies springs from the needs of modern Christian ethics. While there is nothing wrong in this motivation, it may obscure the literary and historical background of the sources: texts to provide proof are excerpted out of their textual and historical context, and they are interpreted to warrant a predetermined ethical position.

J.J. Cadoux's The Early Christian Attitude to War (1919) is a representative example. It was motivated by the horrors of WWI and tried to attest a coherent pacifism in the early church. Cadoux gathered lots of relevant early Christian texts with short comments. Similar text collections were later published with less pacifist leanings. G. finely avoids these shortcomings in his study, which is a thoroughly revised version of his doctoral dissertation defended at the University of Leipzig. He always discusses the time and place of the source texts and reads the textual excerpts in their literary context. He consults a variety of studies on Roman history and early Christianity. In this way G. successfully avoids tendentious explanations. I do not hesitate to say that G.'s work is the most profound study I have read on the topic. The reverse side of the thoroughness is that in 421 pages G. covers only three early Christian theologians: Tertullian, Clement of Alexandria and Origen.

G. is aware of almost every study on early Christianity and military service since the beginning of the twentieth century. Thus, the book serves as an introduction to scholarly work on the topic. A. Harnack's Militia Christi (1905) seems to maintain its position as a recognised classic in G.'s study. G. rightly points out that in the last few decades scholarly positions have been moving towards acknowledging more divergence within the attitudes in the early church. While earlier studies did not deny divergence, they tended to seek one authoritative early Christian position. Scholars with pacifist leanings saw the pre-Constantine Church as a kind of golden era before the Fall. G. shows that there had also been Christian soldiers during the pre-Constantine era. Thus, there was a certain continuity in Christian attitudes between the pre- and the post-Constantine Church. The shift is smoother than the picture of the Fall suggests.

According to G., Tertullian, Clement of Alexandria and Origen belonged to the theological elite whose views did not always agree with the reality in local churches. G. rightly points out that in their attitudes towards soldiers these theologians shared the views of their pagan peers who were usually quite negative towards war and soldiers. On the other hand, this negative viewpoint was not the only truth in the Church, and this also explains certain divergences within the views of theologians. Tertullian is the clearest case in this respect. Scholars have always been at pains to explain why he presents Christian soldiers as positive examples in Apologeticum while in De idolatria and in De corona he is more critical or even utterly negative. Instead of simply noting Tertullian's different positions, G. discusses several explanations provided in earlier studies. G. tries to explain Tertullian's texts in a way that creates a coherent position although he admits the difficulties in his own explanation, too.

Origen's position is as ambiguous as Tertullian's one. The widely cited passage from his works, Origen, Contra Celsum 8.73–4, states that Christians do not take part in warfare. Instead, they contribute to the empire by praying for the emperor and his army. This seems to exclude Christians from all military service. G., however, presents Origen's other texts, which make the situation more complicated. In particular there is one fragment that states that those serving in the army are exempted from the biblical prohibition of using the sword (Matthew 26:52). According to G., Clement is the most unambiguous, and he seems to be the first Christian who speaks of just war. G. also claims that Clement accepts Christian soldiers along with farmers and sailors (Prot. 10.100.4). This may not be true. In the text Clement admonishes the Christian farmer to farm and the Christian sailor to sail, but the one who has become Christian in the army is admonished to obey God. There is no mention of fulfilling the duties of a soldier.

It is also interesting that Clement speaks of a soldier who converts to Christianity. G. makes it clear that early Christians operated a more or less clear difference between those who became Christian while serving in the army and those who were already Christian at enlistment. The former group were more easily accepted while there were also Christian recruits in the Church. G. shows that a military career was attractive for many Christians. At the beginning of the third century there seems to have been a considerable number of soldiers in the Church and in the army. This is also the time when Christians became more visible in several areas of society. G. ponders the need for further study and mentions, for example, the Christian prayer hall in connection with the military camp in Megiddo excavated in 2005. The preliminary report dates the hall to 230, but no further study has been published. However, it suits the growth of Christian visibility at the same time.

G. has penned a profound study on the attitudes towards military service in the writings of three famous early Christian theologians. The cited passages are carefully contextualised, both literally and historically, and G. discusses them extensively and refers to all relevant scholarly literature. There is no clear modern tendency in his study, neither pacifist nor other. G. finely proves that a discussion on early Christian pacifism or non-pacifism is anachronistic as the early theologians studied had a stronger aversion to the imperial religion present in the camp than to bloodshed. Even when rejecting Christian participation in warfare, Tertullian and Origen accepted the pagan army and its warfare for the protection of the empire. However, the increasing number of conversions made this position more and more questionable. Who would serve in the ranks of the Christianised empire? Those pre-Constantine Christians who served in the Roman army paved the way to the future. Still, antimilitaristic views have remained among Christian minorities until the present time. G.'s book is a must-read not only for those who are interested in this topic as a historical matter, but also for those who wish to understand the roots of the ongoing theological discussion on Christian participation in the military.