But our Government seems to have considered the refusal, on the part of
Mexico, to receive Mr. Slidell as a resident Envoy of the United States,
as necessarily leading to war. The Secretary of State, in his letter to
Mr. Slidell of January 28, 1846, says:--"Should the Mexican Government
finally refuse to receive you, the cup of forbearance will then have
been exhausted. Nothing can remain but to take the redress of the
injuries to our citizens, and the insults to our Government, into our
own hands." And again, "Should the Mexican Government finally refuse to
receive you, then demand passports from the proper authority, and return
to the United States. It will then become the duty of the President to
submit the whole case to Congress, and call upon the nation to assert
its just rights, and avenge its injured honor."

With the same object in view, the Secretary of War did, by his letter
dated January 13, 1846, instruct General Taylor "to advance and occupy,
with the troops under his command, positions on or near the east bank of
the Rio del Norte.... It is presumed Point Isabel will be considered by
you an eligible position. This point, or some one near it, and points
opposite Matamoras and Mier, and in the vicinity of Laredo, are
suggested for your consideration.... Should you attempt to exercise the
right, which the United States have in common with Mexico, to the free
navigation of this river, it is probable that Mexico would interpose
resistance. You will not attempt to enforce this right without further
instructions.... It is not designed, in our present relations with
Mexico, that you should treat her as an enemy; but, should she assume
that character by a declaration of war, or any open act of hostility
towards us, you will not act merely on the defensive if your relative
means enable you to do otherwise."

The administration was therefore of opinion, that this military
occupation of the territory in question was not an act of hostility,
towards Mexico, or treating her as an enemy. Now, I do aver, without
fear of contradiction, that whenever a territory claimed by two powers
is, and has been for a length of time in the possession of one of them,
if the other should invade and take possession of it by a military
force, such an act is an open act of hostility according to the
acknowledged and practical law of nations. In this case the law of
nations only recognizes a clear and positive fact.

The sequel is well kn