It is a truth universally acknowledged, that high military ranks bear little risk of falling in battle. However, the junior officer corps were noted for heavy losses in British, French, German, and Austro-Hungarian armies. For example, British officer casualty rates as a whole were about twice as high as those of men in the ranks. (Laurence Housman and Jay Winter, War Letters of Fallen Englishmen, Pine Street Books, 2002, p. v.) The Russian military suffered especially high casualty rates in WWI. By 1917 less than ten percent of the Imperial officer corps were regular officers who had been in the service prior to 1914. (Brian D. Taylor, Politics and the Russian Army, Cambridge University Press, 2003, p. 82 and the references therein.) In a typical engagement during the 1917 Nivelle Offensive, a Russian report placed the death count among their two brigades of infantry sent to fight by the side of the French, at 4472 men and 70 officers. (Jamie H. Cockfield, With Snow on Their Boots: The Tragic Odyssey of the Russian Expeditionary Force in France During World War I, Palgrave Macmillan, 1999, p. 105.)I dont have the data, but it was in fact very rare for anyone who had made captain or above to really be in any danger except to arty.
So much for the safety conferred by noble descent. By contrast, the officer casualty rate for the egalitarian American forces in the Vietnam War was slightly below the enlisted rate. (John Ellis, The Sharp End of War, David and Charles, 1980, pp. 162-64; Richard Holmes, Arts of War: The Behaviour of Men in Battle, Weidenfeld and Nicolson, 1986, p. 350.)