"Animals, Men, and Morals was published in Britain in 1971. My friends and I hoped it would trigger widespread public debate on these issues. Instead, it was ignored. Not a single major newspaper reviewed it. They probably thought it was just another book on animal welfare, a topic of interest only to spinsters living with cats. By 1973, my friends' book was heading for the remainder shelves in Britain. The only spart of hope was than an American edition was about to appear. To try to prevent it from meeting the fate of the British edition, I wrote to the most widely read intellectual journal of the day, the New York Review of Books, and offered them a review essay of the book.
"Animal Liberation" appeared in the New York Review of Books on April 5, 1973. In it, I summed up the ethical position for which I was arguing as follows" "If a being suffers, there can be no moral justification for refusing to take that suffering into consideration, and indeed, to count it equally with the like suffering (if rough comparisons can be made) of any other being." Drawing on the essays in Animals, Men, and Morals, I then showed just how far from this position our practices of animal experimentation and factory farming are."
-- from Ethics into Action by Peter Singer:
Here is Dr. Singer's New York Review of Books article: