Robert N. Meroney, Ph.D. is an Emeritus Professor of Fluid Mechanics and Wind Engineering with a long career at Colorado State University.

In 1844 President James K. Polk was anxious to distract the public from the loss of Vancouver and the northern part of the Oregon Territory to the British, and there was a significant likelihood of war with Britain if the issue was allowed to continue.[1]  Polk preferred a vision of  American “Manifest Destiny” incorporating California, New Mexico and Texas into the United States which would give slavery an area into which it could expand. Lincoln wrote to his law partner William Herndon in 1848 about Polk’s decision to use preemptive war against Mexico.   Lincoln was very opposed to Polk’s expansionist program and made three points:[2]


  1. The president should not start a war because his reasons may end up being wrong.
  2. The president should not start a war because his initiative may start a bigger war.
  3. The Constitution gave congress not the president the power to declare war.  Lincoln noted this was specifically in reaction to the fact that “Kings had always been impoverishing their people in wars, pretending…that the good of the people was the object.  This our Convention understood to be the most oppressive of all Kingly oppressions, and they resolved to so frame the Constitution that NO ONE MAN should hold the power of bringing this oppression on us.” (Emphases shown are Lincoln’s not mine).

Nonetheless, in 1846 Polk had ordered General Zachary Taylor to move troops into the disputed Nueces Strip near the Rio Grande to confront Mexican troops.  The Mexican troops claimed the Americans were on Mexican land and drove off the Americans.  Polk went to Congress demanding they declare war since “Mexican troops had…shed American blood upon the American soil.”

When asked who would pay for the war Polk argued Mexico would pay the costs by ceding California and the New Mexico territories.  Although the U.S. got major territorial expansion as a result of the Mexican American war, we have embittered relations with Mexico now for over a century.  Mexicans even today consider the war an illegal occupation.[3]

It wasn’t much of a “war” really, more like a mugging or a punch in the face.  As Ulysses S. Grant himself finally put it:

I was bitterly opposed to the measure, and to this day regard the war, which resulted, as one of the most unjust ever waged by a stronger against a weaker nation. It was an instance of a republic following the bad example of European monarchies, in not considering justice in their desire to acquire additional territory”.[4]

Did you know that one of the major reasons for the cry for Texan independence that preceded this war was that Mexico had abolished slavery in 1829, and the Texans did not want to give up their slaves?[5]  When you know the back story, all the patriotic guff about the Texas Alamo and the brave American fighters isn’t so impressive.  For example, the so-called hero James Bowie who died in the Alamo was a black birder[6] (slave trader), land swindler and a thief.  Even worse, Bowie was baptized Roman Catholic so he could emigrate to Mexico, he renounced American citizenship and took out Mexican citizenship, married the daughter of the Mexican vice governor of the province, and swore an oath of allegiance to Mexico …so he was essentially a traitor to Mexico when he fought at the Alamo.[7]

So how is preemptive war rationalized?  One definition suggests:

A preemptive war is a war that is commenced in an attempt to repel or defeat a perceived imminent offensive or invasion, or to gain a strategic advantage in an impending (allegedly unavoidable) war shortly before that attack materializes. It is a war that preemptively ‘breaks the peace’.[8]

Preemptive war or preventive war[9] has been embraced by many nations at different times.  Justification has been highly debated.  Most recently for the United States the so-called Bush doctrine was argued to justify the invasion of Iraq in 2002.  In summary, arguments for preemptive response by Bush’s administration were:

  • The nature and magnitude of the threat involved,
  • The likelihood that the threat will be realized unless preemptive action is taken,
  • The availability and exhaustion of alternatives to using force and,
  • Whether using preemptive force is consistent with the terms and purposes of the U.N. Charter and other applicable international agreements.

Article 2, Section 4 of the U.N. Charter prohibits all UN members from even exercising the “threat of use of force against the territorial integrity of political independence of any state.”  In Article 51 the UN Charter draws the line between legitimate and illegitimate military force.  If no attack has occurred, then there is no justification for preemptive “self-defense.”  To be an action of self-defense the preemptive actor must believe the threat is real as opposed to perceived, and self-defensive force must be proportional to the harm threatened.  Even then nonviolent options are preferred such as negotiation, retreat, or calling on neutral authorities like the UN.8 (The United States ratified the UN Charter as of October 24, 1945.)

Sadly, when a nation possesses a first strike advantage and believes it will win a preemptive engagement, there is very little incentive to bargain for any peaceful settlement.  “If the probability of winning minus the probable costs of war is high enough, then no self-enforcing peaceful outcome exists.”[10]

CONCLUSION:  Although patience and time always seems to be a better solution to seemingly terrible danger than war, peace building is not possible if the first reaction is to use a big military hammer because you have it.  With a big hammer everything looks like a nail.

[1] The conflict over Vancouver eventually led to the “Pig War” a bloodless but tense confrontation between the United States and Britain that lasted from 1859 to 1872.

[2] Fehrenbacher, D.E., Ed., Abraham Lincoln:  A Documentary Portrait through his Speeches and Writings, The New American Library of World Literature, Inc., New York, 1964, pp. 59-60.

[3] For the Mexican viewpoint see:

[4] Quote by Ulysses S. Grant about Mexican American War in 1879

[5] Texas Revolution background of slavery and racial bias:

[6] A black birder was a slave trader who kidnaped free blacks and sold them to Plantation owners as being former slaves.

[7] James Bowie:

[8] Chronology of preemptive war to today:

[9] A preventive war as opposed to a preemptive war is one initiated to prevent a belligerent party from acquiring a capability of attacking.

[10] Fearon, James (1995). “Rationalist Explanations for War”. International Organization. 49: 379–414.

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