Amir Khalil, a veterinarian with Four Paws who led the rescue mission, called it an “authentic odyssey.” The animals, he said, will now have proper food and medical care, “without living in constant danger of a nearby war zone and noise of bomb blasts in the background.”

Mr. Khalil visited the Mosul zoo in February to check on the animals and organize regular feedings for them.

His group’s previous attempt to rescue the two animals failed when workers carrying them were stopped at a checkpoint. The aid workers were asked to leave Mosul. Lula and Simba were sent back to the zoo. “We never got to know the exact details why we were not allowed to pass, but, of course, transporting large wild animals in an area with such a complex political situation is not easy,” Mr. Khalil said Wednesday in a telephone interview.

Mr. Khalil said Islamic State militants had been at the zoo and had painted over a sign with the animals’ faces. He said he had heard criticism about his attention to the animals at a time when so many people were suffering. “I like this kind of criticism,” he said, “because in my opinion humanity cannot be divided.”