Diane Ackerman wrote The Zookeeper's Wife based on the real-life memoirs and interviews of Jan and Antonina Zabinski, who used their zoo to help rescue Polish Jews in Warsaw during World War II. An antagonist is any character who fights the protagonist, the story's main character. A couple of different antagonists can be identified in The Zookeeper's Wife. One of the most obvious antagonists is the Nazis who are invading Warsaw and upsetting the lives of our protagonists, Jan and Antonina.
The Nazis are first particularly expressed as an antagonist the moment they begin their Blitzkrieg campaign on September 1, 1939. The people of Warsaw are extremely shocked by Germany's war maneuvers because they had thought their own army was strong enough to defend them and that their allies would come to their rescue. However, at the start of the war, the people of Poland were forced to realize that their "out-numbered, obsolete PZL P.11 fighters posed no match for Germany's fast, swervy Junkers JU-87 Stukas" (p. 50). The antagonist Germany is further described as using a "combined-arms warfare," called Blitzkrieg, which translates to "lightning war," in which every element of warfare possible was used in order to "surprise and terrify the enemy" (p. 50). Hence, the antagonist the Nazis, or the Germans, are described as a physically powerful and crippling force capable of terrifying the protagonist.
A second antagonist is Lutz Heck, a zoologist from Germany, who at first provides Jan and Antonina's zoo with aid but soon sabotages the zoo. First, he advises the couple to send some of their exotic animals to Germany; then, when the zoo is closed, he says he was unable to prevent it from happening. Heck even becomes guilty of organizing a "New Year's shooting party" in which his Nazi friends were invited to hunt the remaining exotic animals on the zoo (p. 95). Hence, Heck is described as being an extremely conniving antagonist.