That is absolutely not true. An easy example to disprove your argument would be the Japanese attack on Pearl Harbor on December 7th, 1941. The American Navy was caught completely by surprise. At the end of the war, there were some Japanese tried for war crimes, but not for the sneak attack on Pearl Harbor.
From what I have read elsewhere, batteries don’t explode. They can heat up and catch fire, but not explode. From what I have read online, a small amount of explosives were added to the pagers plus a very small detonator.