U.S. spy agencies picked up intelligence in mid-June indicating Wagner mercenary chief Yevgeniy Prigozhin was planning armed action against the Russian defense establishment — which he has long accused of bungling the war in Ukraine — and urgently informed the White House and other government agencies so they were not caught off guard, several U.S. officials said Saturday. The exact nature and timing of Prigozhin’s plans were not clear until shortly before his stunning takeover of a military command and tank run toward Moscow on Friday and Saturday, officials said. But “there were enough signals to be able to tell...