The 14-part message that the Japanese ambassador was supposed to deliver to the White House by 1300 was delayed until after 1400 because the message took too long to decrypt. By then the attack on Pearl Harbor had already started and Admiral Yamamoto had no way of knowing the message had not been delivered as planned. While the content of the message didn't really pass as a declaration of war, the fact that the Japanese government issued the message likely meant it knew to comply with the Hague Convention.