https://chroniclingamerica.loc.gov/lccn/sn83045433/1918-05-27/ed-1/seq-1/

The influenza epidemic among the German troops is cited as a reason for the delay in attacking, along  with allied air supremacy and mutinies among the German ranks. The Mercy Fund has passed its goal. Two Chicago packers are accused of shipping beef unfit for human consumption to Camp Travis.

[President Trump's grandfather would die from the influenza epidemic on the day].

Source: "U.S. Fliers Score 3 to 1 Over Hun Airmen," The Washington Herald, Washington, District of Columbia, May 27, 1918. Page 1-2, Column 1.