What is a common theme(s) or idea(s) that Slaughterhouse-Five by Kurt Vonnegut, A Long Way Gone by Ishmael Beah, and Novel Without a Name by Duong Thu Huong share? Can you give any quotes from the books?

Kurt Vonnegut's Slaughterhouse-Five is about an army chaplain's assistant, Billy Pilgrim, who is dispatched to the front lines of World War II in 1944, narrowly survives and returns home to become an optometrist. Decades later, he's the sole survivor of an airplane crash and is hospitalized with an older man who tries to convince him to share stories of the war in a book. However, instead, Billy starts telling tales about being abducted by aliens. For the war sections, Vonnegut draws on his own experiences in World War II, where he served as a soldier during the Battle of the Bulge before being captured and interned at Dresden, to paint a picture of war as a sort of hell on earth.
Ishmael Beah's A Long Way Gone is a memoir that takes place circa 1991 during the Sierra Leone Civil War, when revolutionaries battled government troops for control of the government's valuable diamond mines. Beah's village was attacked when he was a child; his family was murdered, and he spent months surviving in the wilderness before finally being recruited into Sierra Leone's military. Like Vonnegut, Beah draws on his own personal experience to show the atrocities and horrors of war.
Similarly, Duong Thu Huong's Novel Without a Name is a semi-autobiographical account of a female Communist Youth Brigade leader who fought alongside North Vietnamese troops and was one of only three fighters (out of forty) from her brigade to survive. The book's protagonist, however, is a male Communist company commander who has become weary and disillusioned with the war. Like the other books, this one also shows a heavily de-romanticized version of war while attempting to reshape how people view what happened in the jungles of Vietnam.
Despite being written by three very different people living at different times on different continents and fighting in different wars, all three books share similar themes of war-weariness—not just physical fatigue, but mental, emotional, and spiritual—as well as a vision that war itself is nonsensical. Vonnegut sums this up precisely with the line "It is so short and jumbled and jangled because there is nothing intelligent to say about a massacre." In addition, the main characters in each book all seem to be deprived of any sense of control over their life or circumstances. Their choices were already made for them and, as fate would have it, often involved narrowly escaping death. In Beah's book, he writes,

[W]e knew we had no choice, we had to make it across the clearing because, as young boys, the risk of staying in town was greater for us than trying to escape. Young boys were immediately recruited, and the initials RUF were carved wherever it pleased the rebels, with a hot bayonet. This not only meant that you were scarred for life but that you could never escape from them, because escaping with the carving of the rebels' initials was asking for death.

Lastly, the books seem to erode the idea that any side can claim glory from such militaristic pursuits, even the victor. In Thuong's book, Quan's comrades, girlfriend, brother, father, and best friend have all died, and yet he finds himself at a "victory celebration" where he explains that "glory only lasts so long." When a deputy asks him "What happens afterward?" he answers, "How do I know? We're all in the same herd of sheep." In each of the books, there's almost a sense of hopelessness and fatalism even as the protagonists relentlessly continue their pursuit of hope.