Trinity's Child is a novel by William Prochnau. The book depicts a nuclear war waged between the United States of America and the Soviet Union.

In the book the United States has engaged in a massive military buildup, hoping to press the economy of the Soviet Union to breaking point and so force them into political compromise. Instead, the Russian leadership responds by launching a nuclear counter-force strike against America, hoping to destroy their military capability whilst leaving the civilian population relatively intact. In a message to the American President, the Russian Premier offers to accept a similar strike on his own country by the US. It is his hope that such an exchange will allow both nations to survive whilst removing the military threat from America.

Unfortunately great confusion reigns as a result of the attack; the President is believed killed and a low ranking successor with little grasp of the realities of nuclear war is sworn in. Much of the novel depicts the efforts of the surviving US military to end the war with the help of the wounded but still living President against the background of civil chaos caused by the initial exchange. The new President, refusing to accept that his predecessor still lives because he has lost his identification codes in the attack, is determined to defeat the Russians with further nuclear strikes.

The remainder of the book focuses on Polar Bear One, a B-52 on a mission to Russia with a nuclear payload. The book explores the enourmous psychological stress which the crew must endure during the mission - several of the crew crack under this pressure. Ultimately the crew decide to abandon their mission and turn away from Russia. This random act actually assists the peace efforts, as the Russians interpret it as a gesture by the Americans and turn a whole squadron of their own bombers back in response.

Ultimately the new President orders an all out launch of the remaining nuclear arsenal against the Russians, hoping to decapitate the leadership and so avoid retaliation. To prevent this, the original President contacts an Air Force command plane and orders them to rendezvous with Air Force One and ram it before the order can be sent. This is achieved just moments before confirmation of the launch order is transmitted, and further destruction is indeed averted.

The book was made into a television movie, "By Dawn's Early Light". There are some siginificant differences between the two - most significantly, in the movie the initial nuclear exchange is prompted by an accident rather than part of a deliberate Russian plot. This is likely intended to avoid demonising either side as being the aggressor. Another element of the movie is a romantic subplot between the captain of the B-52 and his female co-pilot, something absent from the book.