Here is the story of the link: 

When Fremont started out on his Second Exploration (fairly well dealt with in another chapter), he stopped at the Kansas frontier to equip.  When he finally started, the party (108) was armed generally with Hall’s carbines, which, says Fremont: 

with a brass twelve-pound howitzer, had been furnished to me from the United States arsenal at St. Louis, agreeably to the command of Colonel S.W.  Kearny, commanding the third military division.  Three men were especially detailed for the management of this, under the charge of Louis Zindel, a native of Germany, who had been nineteen years a non-commissioned officer of the artillery in the Prussian army, and regularly instructed in the duties of his profession.

As soon as the news that he had added a cannon to his equipment reached Washington, the Secretary of War, James M. Porter, sent a message after him, post haste, countermanding the expedition on the ground that he had prepared himself with a military equipment, which the pacific nature of his journey did not require.  It was specially charged as a heinous offense that he had procured a small mountain howitzer from the arsenal at St. Louis, in addition to his other firearms.

But Fremont had already started.  He was not far on his way, and the message could have reached him easily.  It was not destined to do so, however, until after his return.  The message came to the hands of his girl-wife, Jessie Benton Fremont, the daughter of Missouri’s great senator, Thomas H. Benton, and she knew, as Charles A. Moody has well written, that

this order, obeyed, would indefinitely postpone the expedition—­probably wreck it entirely.  She did not forward it.  Consulting no one, since there was no one at hand to consult, she sent a swift messenger to her husband with word to break camp and move forward at once—­“he could not have the reason for haste, but there was reason enough.”  And he, knowing well and well trusting the sanity and breadth of that girl-brain, hastened forward, unquestioning, while she promptly informed the officer whose order she had vetoed, what she had done, and why.  So far as human wit may penetrate, obedience to that backward summons would have meant, three years later, the winning of California by another nation—­and what that loss would have signified to the United States none can know fully, but any may partly guess who realizes a part of what California has meant for us.

In commenting later upon this countermand of the Expedition Fremont remarks: 

It is not probable that I would have been recalled from the Missouri frontier to Washington to explain why I had taken an arm that simply served to increase the means of defense for a small party very certain to encounter Indian hostility, and which involved very trifling expense.  The administration in Washington was apparently afraid of the English situation in Oregon.