THERE IS probably no movement so little understood by its direct descendants as the American missionary movement at the turn of this century. Two world wars and continued rumors of nuclear holocaust have made us unable to comprehend the kind of optimism and single-minded belief that sent thousands of American youth to foreign lands with the battle cry: "The evangelization of the world in this generation!"

The Call is the story of one of these who, as a student at Syracuse University, received "the call" to service in China under the auspices of the Young Men's Christian Association. In 1905, David Treadup, equipped with a campus conversion experience, a hard won bachelor of science degree, physical stamina and the ebullient enthusiasm of tha day, went out, like Abraham, "not knowing whither he went." It was not considered important in those days knowing about China. What China was did not matter. Whatever she was, these elected youth were going to change her.

Yet it was China that ground away at their enthusiasm, that broke their health, that revealed the shallowness of their education and culture, that seemed, like the inexorable devastation of her rivers, to wash away any evidence that their heartbreaking toil had made the slightest inroad into the vastness of human suffering that China had been, was now and surely would remain.

As year follows year, disaster upon disaster, war upon war, Treadup is given to rephrasing the original battle cry. It becomes: "The education of China's millions in this generation!" "For Jesus Christ's sake, the abolition of poverty in this generation!" The brave cry drops to a whisper: "to ease the human suffering of a few people near at hand." It turns ironic: "Modernize the Yin Hsien (Japanese detention) Camp in this generation!"

The slogans reveal the progression of the novel. The proud young university graduate, chastened by years of struggle to evangelize the literati of China, first through teaching and preaching, and then through lectures on science, abandons the rich for China's poor. His large, if not always wise heart, goes out to those millions who "eat bitterness" as a steady diet. Perhaps if they learned to read? He goes into the peasant villages and organizes literacy schools. But the people are still miserable. Perhaps if they learned how to farm more efficiently? He helps the villagers improve their farming techniques, dig communal wells, raise healthy stock. But what floods and drought do not destroy, armies do. He writes in a letter to his brother: "Here in China one who tries to hold on to his faith moves inevitably toward the Book of Job."

HERSEY HAS written the story of David Treadup as a "fictionalized biography" with excerpts from diaries, letters and personal papers. There is a slight distance in the writing, a biographer not being privy to all the information available to a novelist. We do not, for example, know the details of David and Emily Treadup's sexual relationship, but we can infer that it was a source of comfort and delight to them both. The style provides a reticence, rarely found in today's novels, which is absolutely appropriate for this story.

I suppose no one should marvel at how elegantly constructed this book is. We expect a master to perform in a masterly fashion, but the material Hersey has chosen to work with is the kind that confounds even the best writers. Hersey's father was a YMCA missionary to China and appears as a minor character in the book. So although David Treadup is deliberately not Roscoe Hersey, the book must have involved the writer in an examination of the meaning of his father's life.

Pearl Buck's biography of her missionary father, The Fighting Angel, comes immediately to mind. Andrew Sydenstricker and David Treadup worked in China during much of the same period of history. Both men were regarded with some suspicion by their colleagues. Missionaries who lived too closely to the Chinese were not popular with their own kind. However, when the stories are compared, Hersey's fiction seems to be the work of meticulous scholarship, while Buck's fact emerges as a sometimes patronizing, occasionally sentimental memoir by a daughter who did not know her father very well. In addition, Hersey has somehow managed to retain in his "biography" the emotional impact and pleasure of fiction -- the best of both worlds.

In a Japanese detention camp, cut off from the peasants for whom he gave his life, and from Emily who sustained that life, David Treadup loses his faith. A curious expression, that. Only a people who have a portable god could speak as though God were something that might be misplaced. But however understood, Treadup is unable to share this loss. When he returns to her in 1943, he finds an Emily too fragile for the burden of such a confession. After the war and Emily's death, he returns to China and is eventually expelled by the communists for a belief he no longer holds.

So did his life in China become "utterly without influence and futile?" Did China defeat those brave, naive, impatient soldiers for Christ just as she eventually defeated all her invading armies over the last 3,000 years?

It might comfort David Treadup to know that those same communists who denounced and expelled him have put into practice the approaches to literacy and farming that he and his Christian colleagues introduced years ago. He would want to know that some of the misery that broke his heart has been alleviated.

But surely it would amaze him that the faith he lost has been found. The church most Westerners despaired of has emerged after 30 dark years alive and strong like Jonah from the belly of the whale. Perhaps the time has come for the children of those who sought to change China, to look to China to change us. We might learn patience from a people for whom 400 years is but a day. Perhaps we might even learn from those who have truly eaten the bitterness of poverty and ignominy and persecution how to endure in the face of the impossible.