Since many events are planned here in France for the 100 years of the start of WW1, I’ve had a little look at the impact on french mathematicians at the time.
Several historians of mathematics have produced over the past few years many interesting books and papers (many in english, for wider readership).
I have noticed that Laurent Mazliak has an interesting paper on René Gateaux, who died in 1914 aged 25, even before completing his PhD. Mazliak also has a book in collaboration with Rossana Tazzioli on the intense correspondance between Vito Voltera (who wanted Italy to join the conflict, and himself fought in the trenches aged 55) and several french mathmaticians (Borel, Hadamard and Picard).
David Aubin also has several interesting papers on the topic. One discusses what happened to students of Ecole Normale Supérieure. A few months ago Aubin published three more papers (all will appear in a book to be published by the AMS): with Catherine Goldstein this long one on the general setting beyond the french perspective, with Goldstein and Hélène Gispert that one centred on parisian mathematicians, and a last one on ballistics.
Between 2003 and 2008, a seminar was held with many more contributors.