The gas attack on the 1st Division on 28 - 29 March was probably one of the first on American troops in which diphenylchloroarsine (blue cross) was used, and though it was recognized as such by the Division Gas Officer, the new gas was not remarked by anyone else reporting on the attack. Just the day before this attack, an operations memo reported that "the enemy has a blue cross shell which emits smoke, not in itself poisonous, but composed of small particles which penetrate our masks, and irritate the throat and lungs. These shells are always followed by poison gas shells" [i.e., phosgene or diphosgene - green cross].90
As a matter of fact, the blue cross shell was not new. Small quantities of it were first introduced on the British front in the summer of 1917, with good results. The Germans appear to have thought so highly of the shell that they at once put it into mass production, turning out vast numbers of both blue cross and colored or variegated (Buntkreuz) shells, the latter containing
both phosgene and diphenylchloroarsine.91 The blue cross shell was apparently the secret weapon for the spring offensives of 1918, for they were apparently first used in great quantities in the attack of 21 March. Two months later, after the introduction of the ethyldichloroarsine shell (yellow cross-l), these two gas shells were to comprise as high as 70 percent of the gas fired in preparation for the attack launched from the Chemin des Dames on 27 May.92
Few besides gas officers seem to have been immediately aware of the new gases. Lieutenant Butler, for example, never mentions them but refers only to the three gases of AEF pamphlet 253, chlorine, phosgene, and mustard gas; and G - 2 speaks of "gas resembling chlorine, "a gas causing nausea, sneezing and coughing," and "sneeze gas."93 "Sneeze gas," though sometimes applied to chloropicrin, became the common name for the arsines. It was June before a reference in an intelligence report is found to "Chlorine Arsine and Bromine Arsenic."94
The 1st Division was to be in Picardy when the great German offensives of May and June were launched in that area. But a whole week passed after being ordered to that front before the division cleared the sector at Ansauville.