Prime Minister Shinzo Abe’s conservative government has begun to pursue a more openly nationalist agenda on an issue that critics fear will push the country farther from its postwar pacifism: adding a more patriotic tone to Japan’s school textbooks.

The proposed textbook revisions have drawn less outcry abroad than Mr. Abe’s visit on Thursday to a shrine that honors war dead, including war criminals from World War II. However, though Mr. Abe’s supporters argue that changes are needed to teach children more patriotism, liberals warn that they could undercut an antiwar message they say has helped keep Japan peaceful for decades.

“Prime Minister Abe is feeling the heat from his political base, which feels betrayed that he has not pursued a more strongly right-wing agenda,” said Nobuyoshi Takashima, a professor emeritus at the University of the Ryukyus in Okinawa who has studied the politics of textbooks. “Classrooms are one place where he can appease ultraconservatives by taking a more firmly nationalist stance.”