Does he have a pair of yiddies depicted in this? Is there a reason?

Yes.

The cartoon is targeted at Rosa Luxemburg who was a German, Jewish, communist/socialist activist during the WW1 era. The cartoon implies that her activism was the equivalent to stabbing the German soldiers in the back, causing their defeat in WW1 (in this case she is a representative of the larger JEwish socialist cohort, not singled out to be the sole responsibility. Sort of like using someone like Greta Thurnburg as a stand in for all environmentalists.)