In 1846, the United States went to war with Mexico,... Show more
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Dec 18, 2025
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Was the United States Justified in the Mexican-American War?
O
Oscar Crimaldi
@oscarcrimaldi_pvih
1 / 4
The Road to War: Manifest Destiny and American Expansion
Ever wondered how the US acquired so much territory in the West? It wasn't always peaceful. In 1846, tensions between the United States and Mexico erupted into full-scale war, largely driven by Manifest Destiny – the belief that American settlers were divinely destined to expand westward across North America.
The conflict had been brewing for years. When Texas declared independence from Mexico in 1836 and was finally annexed by the US in 1845, Mexico was furious. The countries also disputed the location of the Texas-Mexico border – the US claimed it was at the Rio Grande, while Mexico insisted it was at the Nueces River, significantly farther north.
On May 9, 1846, news arrived that Mexican soldiers had fired on American troops along the Rio Grande. President James K. Polk quickly asked Congress for a declaration of war, which the Senate approved by an overwhelming 40-2 vote. But this seemingly straightforward decision had complex and questionable motivations.
Think About It: Was this truly a defensive war as claimed, or did the US deliberately provoke Mexico to gain territory? The answer involves politics, slavery, and territorial ambition.
President Polk's Provocations
President Polk didn't stumble into war by accident – he practically engineered it. As a firm believer in Manifest Destiny, Polk had his eyes set on Mexican territory from the beginning of his presidency. When diplomatic attempts to purchase land from Mexico failed, he took more aggressive steps.
Polk deliberately sent American troops under General Zachary Taylor into the disputed territory between the Nueces River and Rio Grande. To Americans, this was "American soil," but Mexicans viewed this as a clear invasion of their territory. When Mexican forces fired on Taylor's troops, killing sixteen American soldiers, Polk had the perfect excuse to ask Congress for a war declaration.
From Mexico's perspective, they weren't starting a war – they were defending their territory from foreign invasion. The conflict had fundamentally different interpretations: Americans saw themselves as victims of unprovoked attack, while Mexicans believed they were rightfully defending their sovereignty against American aggression.
This war wasn't about defending American borders as Polk claimed. His actions revealed a calculated strategy to provoke Mexico into conflict for territorial gain – hardly a justifiable reason for war.
Slavery's Shadow Over the War
The Mexican-American War wasn't just about gaining territory – it was about what would happen on that territory. When Americans moved into Texas before its annexation, they brought their slaves, despite Mexican laws prohibiting slavery.
As Charles Sumner wrote in 1847, "Slaveholders crossed the Sabine with their slaves, in defiance of the Mexican ordinance of freedom." The war represented a troubling expansion of the slave system at a time when the institution was becoming increasingly controversial in American politics.
This reality exposes a profound contradiction in American values. The nation that proudly proclaimed "all men are created equal" was fighting a war that would extend slavery's reach. The Mexican-American War essentially advanced an institution that Mexico had already abolished, making America's justifications for war even more questionable.
Connection Point: The territories gained in this war would later become central to the debates that led to the Civil War. The question of whether slavery would be allowed in these new lands intensified sectional tensions.
American Greed and Historical Legacy
At its core, the Mexican-American War was driven by American greed – a hunger for land without consideration for other nations' sovereignty or the consequences of expansion. Unlike Polk's claims about "defense," the true motivation was territorial acquisition, fueled by the belief that expansion was America's divine right.
The different names for this conflict reveal its contested nature. Americans call it the "Mexican-American War," while Mexicans refer to it as "The U.S. Invasion." As author Jesus Velasco-Marquez wrote, "From Mexico's point of view, the annexation of Texas to the United States was inadmissible for reasons."
The war resulted in approximately 13,000 deaths and dramatically altered North America's map. The United States gained California, Nevada, Utah, and parts of Colorado, Arizona, New Mexico, and Wyoming – about half of Mexico's territory. While these regions became integral to modern America, they came at the cost of deception, aggression, and disregard for Mexican sovereignty.
Though we now take these western states for granted as part of America, their acquisition came through questionable means. The war may have expanded American territory, but it did so through actions that contradicted American ideals of justice and respect for other nations.
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Brad T
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Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
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The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
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Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
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This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Was the United States Justified in the Mexican-American War?
O
Oscar Crimaldi
@oscarcrimaldi_pvih
In 1846, the United States went to war with Mexico, claiming territories that would later become key parts of the American West. This conflict emerged from the concept of "Manifest Destiny" and America's aggressive westward expansion. But was this war... Show more
The Road to War: Manifest Destiny and American Expansion
Ever wondered how the US acquired so much territory in the West? It wasn't always peaceful. In 1846, tensions between the United States and Mexico erupted into full-scale war, largely driven by Manifest Destiny – the belief that American settlers were divinely destined to expand westward across North America.
The conflict had been brewing for years. When Texas declared independence from Mexico in 1836 and was finally annexed by the US in 1845, Mexico was furious. The countries also disputed the location of the Texas-Mexico border – the US claimed it was at the Rio Grande, while Mexico insisted it was at the Nueces River, significantly farther north.
On May 9, 1846, news arrived that Mexican soldiers had fired on American troops along the Rio Grande. President James K. Polk quickly asked Congress for a declaration of war, which the Senate approved by an overwhelming 40-2 vote. But this seemingly straightforward decision had complex and questionable motivations.
Think About It: Was this truly a defensive war as claimed, or did the US deliberately provoke Mexico to gain territory? The answer involves politics, slavery, and territorial ambition.
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President Polk's Provocations
President Polk didn't stumble into war by accident – he practically engineered it. As a firm believer in Manifest Destiny, Polk had his eyes set on Mexican territory from the beginning of his presidency. When diplomatic attempts to purchase land from Mexico failed, he took more aggressive steps.
Polk deliberately sent American troops under General Zachary Taylor into the disputed territory between the Nueces River and Rio Grande. To Americans, this was "American soil," but Mexicans viewed this as a clear invasion of their territory. When Mexican forces fired on Taylor's troops, killing sixteen American soldiers, Polk had the perfect excuse to ask Congress for a war declaration.
From Mexico's perspective, they weren't starting a war – they were defending their territory from foreign invasion. The conflict had fundamentally different interpretations: Americans saw themselves as victims of unprovoked attack, while Mexicans believed they were rightfully defending their sovereignty against American aggression.
This war wasn't about defending American borders as Polk claimed. His actions revealed a calculated strategy to provoke Mexico into conflict for territorial gain – hardly a justifiable reason for war.
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Slavery's Shadow Over the War
The Mexican-American War wasn't just about gaining territory – it was about what would happen on that territory. When Americans moved into Texas before its annexation, they brought their slaves, despite Mexican laws prohibiting slavery.
As Charles Sumner wrote in 1847, "Slaveholders crossed the Sabine with their slaves, in defiance of the Mexican ordinance of freedom." The war represented a troubling expansion of the slave system at a time when the institution was becoming increasingly controversial in American politics.
This reality exposes a profound contradiction in American values. The nation that proudly proclaimed "all men are created equal" was fighting a war that would extend slavery's reach. The Mexican-American War essentially advanced an institution that Mexico had already abolished, making America's justifications for war even more questionable.
Connection Point: The territories gained in this war would later become central to the debates that led to the Civil War. The question of whether slavery would be allowed in these new lands intensified sectional tensions.
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Access to all documents
Improve your grades
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By signing up you accept Terms of Service and Privacy Policy
American Greed and Historical Legacy
At its core, the Mexican-American War was driven by American greed – a hunger for land without consideration for other nations' sovereignty or the consequences of expansion. Unlike Polk's claims about "defense," the true motivation was territorial acquisition, fueled by the belief that expansion was America's divine right.
The different names for this conflict reveal its contested nature. Americans call it the "Mexican-American War," while Mexicans refer to it as "The U.S. Invasion." As author Jesus Velasco-Marquez wrote, "From Mexico's point of view, the annexation of Texas to the United States was inadmissible for reasons."
The war resulted in approximately 13,000 deaths and dramatically altered North America's map. The United States gained California, Nevada, Utah, and parts of Colorado, Arizona, New Mexico, and Wyoming – about half of Mexico's territory. While these regions became integral to modern America, they came at the cost of deception, aggression, and disregard for Mexican sovereignty.
Though we now take these western states for granted as part of America, their acquisition came through questionable means. The war may have expanded American territory, but it did so through actions that contradicted American ideals of justice and respect for other nations.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user