I haven't been able to find anything specific re Tyler's orders but in Fremont's first expedition in 1843-44
IOTL his orders from the Army merely stated he was to examine the Oregon trail for the benefit of
those who would use it in the future. His orders from Polk however, are a rather murky business. JCF
set out for California on what was his third expediton there in December 1845. Apparently- yes, here is the rub- he was ordered only to do more surveying, & he did not have any WRITTEN instructions to stir
up an anti- Mexican revolt. But it seems that unofficially, members of Congress told him that if the U.S. & Mexico were @ war when he got to California the he was to do all he could to keep California out of
British hands, & instead make sure it became a part of the U.S. Navy Secretary George Bancroft, also
in private, said pretty much the same thing to JCF. Later JCF stated he received secret messages from Marine Corps Lt. Archibald Gillespie. These messages directed Fremont to abandon his
surveys & stay in California. We do know that Gillespie orally told the US Consul in California,
Thomas Larkin, that Larkin was now to arrange for California to separate from Mexico(to later,
like Texas, join the U.S). Now there is no existing documentary evidence for all this. Fremont had
taken 60 sharpshooters with him, a very strong force @ that time & place(why did JCF
do this?) He then did proceed to en-
courage American settlers to rise up against Mexico(the so-called Bear Flag Revolt)& teamed up
with other army & navy forces to win California from Mexico, thus indeed paving
the way for it to become an American state.
To reiterate, he had, it seems, no written authority to do so. Is this what the CIA would one day call "plausible deniability"? Was JCF actually acting as a secret agent for Polk? Or did JCF just plain disobey orders that he should not fight & just stick to
surveying? It's still disputed. At any rate, Fremont was court-martialled for his actions in California, found guilty of mutiny & disobedience- & then pardoned by Polk.
I hope you'll find this to be of help 2fisted.
SOURCES: CALIFORNIA: LAND OF NEW BEGINNINGS by David Lavender(1987), THE JACK-
SONIAN ERA by Glyndon Van Deusen(1959), PROFILES IN CHARACTER by Joseph M Hernon
(1997), SO FAR FROM GOD: THE U.S. WAR WITH MEXICO 1846-1848 by John S.D. Eisenhower
(1989), SPYING FOR AMERICA by Nathan Miller(1989), & THEY ALSO RAN by Irving Stone,
paperback edition(1964).