Jürgen Moltmann is a German Reformed Theologian, and was a soldier in the Nazi Germany Army. However, when Moltmann learned about the Nazi concentration camps, especially Auschwitz, he then surrendered to the first British soldier he encountered. While a prisoner of war, an army chaplain for the British army gave him a slimmed down bible, similar to a Gideon's bible. As Moltmann said it, "I didn't find Christ, he found me." He went on to receive his Ph.D. and wrote many influential, yet controversial books due to being influenced by Karl Barth, Hegel, Tillich and others. There's also an anecdote in his biography, that he had read a book by one of the Niebuhr brothers, and it was his only access to Christianity that caused him to head towards a future in theological academia.
I don't know how accurate that biological sketch is, because not much of it was covered in the only book I've read by Moltmann: The Crucified God. Moltmann primarily engages Luther and the Calvin quotes were kept to a minimum, and since he was a professor at the German Tübingen School, I don't know how reformed he actually may be, since he engages Lutheran ideas and theologians more often than the Reformed crowd. He's still alive, so I could probably use google translator to email him!
Auschwitz and Hiroshima are certainly at the center of Moltmann's thought, especially considering one of his books is titled "A Theology of Hope." Considering the crisis of the two great world wars, many today equate "hope" with universalism, but I overlooked any conclusions in this topic in The Crucified God.
Martin Luther is at the center of the Crucified God, for Luther took up the phrase "The Crucified God" first used by early church fathers and popularized it. It is a controversial and shocking title, and Moltmann explains that the way we know Jesus is through the Cross, but also the way that Jesus knows the Father is through the cross as well. Moltmann even accused Barth of not being trinitarian and having a trinitarian view of the cross at the center of our understanding of God. In a fully trinitarian view, we may identify Jesus as God on the Cross crucified, without the difficulties of patripassianism. (However, Moltmann doesn't appear to have a problem with saying that the Father suffered in Jesus on the Cross within a trinitarian concept, because how else could the Father love or could God be love, he argues.) I'll have to read Moltmann's book on the Trinity to find that answer.
The dominant theme of the book however is Luther's "Theology of the Cross", and in direct contrast to the ever popular, "Theology of Glory". Moltmann returns to this topic a myriad of times, giving me a greater appreciation for the revolutionary thought of Martin Luther's Heidelberg Disputation (1518). Moltmann goes so far as the critique the Cosmological Argument as a Theology of Glory and says it is not in the greatest first cause (paraphrase), but the humility and suffering in the cross that we find the true revelation of God.
Moltmann returns many times to the "Brother Karamazov" by Dostoevsky. In the book, at a concentration camp, a group of men are hanged including a youth, and one of the crowd says "Where is God?" in reaction to the length it takes for the youth to die. Moltmann says that in light of Hiroshima and Auschwitz, we may respond "Christ is there dying with that youth on the gallows" (paraphrase).
Another theme is Moltmann's constant question, "Have we replaced our Christology with Jesusology", in other words, have we given up the eschatological king Jesus, and changed Jesus into a timeless teacher of moral truths, or reduced him to only a good example, but rather have we seen him truly as the immanent eschatological king. Moltmann equates the gospel with having correct Christology. A wonderful challenge. If Jesus was truly man, made of spirit and body, then his death on the cross mean spiritual and physical death.
Another topic, was Moltmann's insistence in the historicity of Christ, because when we contextualize Christ, we have changed him from what he was into something new and relevant, and thereby leaving the historical faith in the dust (paraphrase). The problem is that Christianity is a historical faith, based on the historical event of the Cross, so every time we change what was said from the beginning to say something new, in many ways we have abandoned what it originally was.
What an amazing book! It's one of the few books this year that I've read that I cannot stop thinking about, and I read a lot! Do I recommend this as a confession of faith? Not yet! You must read this book critically, but many wonderful ideas are in this volume that I'd encourage you to pick it up and really think about the Cross for today.
Related: Jürgen Moltmann, The Crucified God