its chance to acquire the Lone Star
Republic.
On February 28, 1845, before Polk
had been inaugurated, the U.S. Congress
approved a joint resolution inviting Texas
into the Union. Mexico protested and
broke off diplomatic relations with the
United States, but the tide of U.S. expan-
ionist sentiment grew. In the summer of
1845, John L. O’Sullivan, editor of the
United States Magazine and Democratic
Review, coined the phrase Manifest
Destiny, saying it was the United States’
“manifest destiny to overspread the conti-
nent allotted by Providence for the free
development of our yearly multiplying
millions.” O’Sullivan had not originated
this idea; many Americans, including
Polk, felt that their country should and
would expand from coast to coast, bring-
ing with it the blessings of democracy and
free enterprise. Some saw no limits to this
destiny—up into Canada, down into
Mexico, even into South America or
Europe. One American soldier wrote
prior to the U.S.-Mexican War that with
a “gigantic effort” the United States
“could sweep the continent from Panama
to the Pole and from ocean to ocean in a
year.” Others, like Polk, were more
restrained; they wanted only North
America, from sea to shining sea.
Manifest Destiny was closely linked
to the commonplace racism of the day: the
view that white Anglo-Americans were
superior to the darker-skinned Native
Americans and Mexicans currently occu-
pying the coveted lands. Many Americans
viewed it as an outrage that a people like
the Mexicans, whom they regarded as
lazy and degenerate, should stand in their
way. Sam Houston wrote that he could
“see no reason why we should not go in... and take their [the Mexicans’] lands.”
Polk made one major effort to
acquire the Far North peacefully. In
November 1845 he sent diplomat John
Slidell (1793–1871) to Mexico to try to
gain recognition of the Rio Grande bor-
der for Texas and buy New Mexico and
California. As a bargaining tool, Slidell
was to use claims of damages to American
property during Mexico’s civil wars, claims
that the United States was willing to drop
in return for Mexican cooperation. The
Mexicans adamantly refused to negotiate
with him.
While Slidell was in Mexico, Texas
entered the Union, becoming the 28th
state on December 29, 1845. At about the
same time, another revolt broke out in
Mexico, with General Mariano Paredes
coming to power on January 2, 1846. As
Polk saw it, he had tried peaceful means
to acquire Mexico’s Far North, and those
had failed. His next move was war.War with Mexico
On January 13, 1846, Polk ordered
General Zachary Taylor and his 3,550
troops to advance from their position on
the Nueces River to the Rio Grande. The
president did so knowing that Mexico
rejected the American claim to the territo-
ry between the rivers and would therefore
regard this move as an invasion. On March
28 Taylor arrived at the Rio Grande,
across from the Mexican city of
Matamoros, and began constructing forts.
Shortly thereafter, General Pedro de
Ampudia, commander of Mexico’s
Division of the North, ordered Taylor to
withdraw or face hostilities. Taylor refused.
On April 25 a large Mexican cavalry
force crossed the Rio Grande. They sur-
rounded a small squadron of American
dragoons, killing or wounding 16 and
taking the rest prisoner. Taylor sent word
to Polk, who informed Congress heated-
ly, “Mexico has passed the boundary of
the United States, has invaded our terri-
tory and shed American blood upon the
American soil.” Some congressmen
objected, questioning whether the east
bank of the Rio Grande could really be
considered American soil, but they were
in the minority. Congress declared war on
Mexico on May 13, 1846. A subordinate
of Taylor’s, Colonel Ethan Allen
Hitchcock, commented: “It looks as if the
government sent a small force on purpose
to bring on a war, so as to have a pretext
for taking California and as much of this
country as it chooses.”
The American strategy for winning
the war centered on Taylor, who had won
two victories on the northern side of the
Rio Grande even before the declaration
of war: at Palo Alto on May 8 and Resaca
de la Palma on May 9. On May 18 Taylor
advanced into Matamoros, which the
enemy had abandoned, and raised the
American flag there. The plan was for
Taylor to keep pushing into northern
Mexico, while a separate force, the Army
of the West, conquered New Mexico and90 ATLAS OF HISPANIC-AMERICAN HISTORY