The border wall can play a great role. Build one in the north and one in the south to isolate Canada and Mexico. It can eliminate many troubles, such as drugs and illegal immigrants.
In Chinese history, until 1840, the Great Wall was the main fortification for the annoying nomads in the north. Its first function was alarm and communication. In ancient times, there was no telephone, so the most effective way to convey the information that nomads were invading was wolf smoke, which might convey the information to the headquarters in one day, and the army could assemble. In this way, when the barbarians reach the wall on the ridge after the long march and are exhausted, they will find a strong army preparing for battle.
Some smart savage chiefs were very smart and came up with the idea of bypassing the city wall, avoiding the Han Army and launching a sudden attack. But when they reached the end of the wall, they would find the Han Army waiting for them. Why? Because it is easier for the Han Army to walk on the wall, while the barbarians can only march in the wild with mountains and marshes.
Since the nomads had only one trade option, the Han people, they could not forge metal products. The emperor of the Han Dynasty could impose severe economic sanctions on them with the Great Wall. They just issued orders to ban all trade and waited for the nomads to exhaust their iron arrows and their military strength became weak, so that the Central Plains Dynasty could achieve its strategic goal without a single soldier.
For example, after Zhu Yuanzhang of the Ming Dynasty chased the Mongolian rulers north of the Great Wall, Mongolian tribes used bone arrows within 30 years, not to mention important things such as salt and tea. Few individual smugglers can cross the wall through patrols. Therefore, the third function of the wall is economic blockade.
So in short, the Great Wall is very effective against northern nomads such as Huns, Mongols and Turks.
The Song Dynasty lost the Great Wall, so it was always weak until its demise. The Ming dynasty built the Great Wall, so it was able to win the northern military victory.
Arrogance and ignorance will lead to the destruction of a great empire.
Before the industrialization of the west, China has always been the leading force in the known world. It believes that its way of doing things is the best in the world, and therefore has no interest in understanding the world outside China.
They will think, "for thousands of years, we Chinese have been doing things according to our own traditions. How can these barbarians teach us good things?" Of course, arrogance and ignorance will lead to social stagnation - no reform, no change... Only after the British appeared and drove them away did they pay the price for their arrogance.
Now, some Westerners I meet seem to have the same mentality as the Chinese in the late Qing Dynasty... Obsessed with "democracy! Freedom and human rights! America first!" In the beautiful lies drawn.
They are full of such thoughts: "what do you brainwashed who have no taste for democracy and freedom know?! 10% GDP growth rate? It must be false. They are too afraid to say what they think. They must be eagerly waiting for the Western savior to rescue them from their suffering...".
"Chinese people can't innovate. China has built the world's fastest computer with its own CPU? The quality of research papers published by China ranks second in the world, roughly equal to that of Germany and the UK combined? In 2014, China received US $15.5 billion in venture capital, about 50% higher than the US $10.6 billion obtained by Europe in the same period, although the economic scale of the EU is larger than that of China? Venture capitalists of Sequoia and KPCB Don't you know that innovation is only possible in democratic countries? "
"Well... I only know that China is only suitable for making cheap toys that always break down, so these news must be exaggerated propaganda by China, otherwise I will pretend not to hear it. Anyway, China will collapse one day, and the stupid things I hear about China that are not in line with my world view will disappear..."
The United States has no exception theory, just as the Romans, Britons, Turks and Chinese have no exception theory. Arrogance + ignorance always leads to the destruction of all once great empires without exception.
First, a country that is too conservative will eventually lag behind others. Although I doubt the possibility that the United States will be invaded soon, it must be slowly declining, in part because the United States seems to adopt a culture that advocates rigidity rather than openness. It seems that there is a general tendency to believe that American philosophy has found the perfect answer to everything eternal, so there is absolutely no need to change.
-Everyone is trying to reduce climate change? Sorry, it will damage our economy and affect our work. Do they even suspect that climate change is caused by human activities?
-Is everyone trying to improve or implement universal health care? Sorry, this is socialism. Everything related to socialism is taboo in the United States.
-Trying to narrow the gap between the rich and the poor? Sorry, this is contrary to the American dream and runs counter to capitalism in principle.
When it comes to the economy, if you spend money on the wrong things, if only a few people can benefit from it, it doesn't matter how rich your country is or how good the economy is.
At almost every moment in history, China is one of the richest countries on earth. Even before the Sino Japanese war in 1895, China was much richer than Japan. If empress Cixi didn't spend all her imperial budget on luxury, China could have built a better Navy. The Song Dynasty was no poorer than the Mongols and the Ming Dynasty was no poorer than the Manchus, but both failed because the former spent money on luxury and pleasure, while the farmers were starving to death.
Today, the richest 1% of Americans own about 40% of their national wealth, while the bottom 40% are trying to get enough food to avoid hunger. We don't even have to talk about their health care and other needs. Most students who decide to go to college will be in debt after graduation. The money spent on the military in this country is astronomical, but in improving the environment, education system, medical system, crumbling infrastructure The situation of many veterans and the elderly is frequently in arrears.
Therefore, the biggest enemy of a big country like the United States is likely never to be foreigners. The biggest enemy of the United States almost always comes from home. The biggest enemy that led to the collapse of many big countries was party politics.
When you put the interests of the party above the state, you will do something in favor of the party at the expense of the interests of the state. In China's long history, internal conflicts have led to the collapse of too many dynasties. In fact, the downfall of almost every dynasty was caused, at least to some extent, by internal conflict. When you carefully observe the current political situation in the United States, you can easily realize that there are problems in some places. The two major political parties always seem to be blindly opposed to each other.
During Obama's two terms in office, Republicans opposed almost all his proposals and did not even analyze whether his proposals would help the country. Then there is trump, whose only goal in the white house seems to be to overthrow what Obama has done, no matter what. If this is the political atmosphere of a country, how can it work normally? I mean, look, Republicans and Democrats have good and bad aspects on different issues, so it's best to choose their respective advantages to form a good plan, but in the current political atmosphere, this is almost impossible.
Since the an Shi rebellion, the Tang Dynasty has experienced a strategic contraction due to the increasing external threats such as Tubo, Khitan Confederation and Nanzhao kingdom. Therefore, the Tang Dynasty formed a complex relationship with military regions and legions. On the one hand, the Tang government needed the military region's Jiedu envoy to deal with external threats. On the other hand, the need for a large amount of military spending to win the loyalty of professional soldiers who often disobey discipline has become a huge financial burden on the central government.
The soldiers of the Mid Tang, Five Dynasties and Ten Kingdoms periods were famous for their disobedience, arrogance and aggression. The armor, utensils and paintings of this period vividly reflected the characteristics and behavior of the military class.
Today, we see a similar trend in the United States. As the decline of US hegemony contrasts with the rise of foreign forces (China, Russia, Iran, North Korea, Turkey, India...), trump is promoting global strategic contraction. The United States is undergoing a great transformation from a universal empire to a nationalist country. However, trump had to announce a substantial increase in the defense budget, including the upgrading and purchase of weapons and an increase in the wages of soldiers.
This seems controversial, and liberals may interpret it as trump going crazy again. However, this reflects not trump's madness or "China's threat", but the political and economic reality of the United States.
The reality is that US political leaders must win the support and loyalty of increasingly influential military factions and classes (military industrial complex). A global empire with accumulated historical, internal and external interests has made the military a huge profit hungry industrial and popular group, which, in my opinion, is strong enough to threaten the position of the president.
On the other hand, since the disappearance of self-made manufacturing industry, the financial hegemony of the United States has been based on military hegemony. The United States needs the army to maintain its hegemony, but this service and industrial ecosystem is not free.
Therefore, the United States is facing the same dilemma as the Tang Dynasty in terms of military factions and classes. Soon, structural conflicts will erupt if the US economy and government budget cannot support huge spending. How to deal with these challenges will be a difficult task for Biden and future leaders.
There was a well-designed and complex bureaucracy in the Tang Dynasty. Laws, supervision and checks and balances were used to restrict the army, generals and soldiers. It was not a system problem, but a problem of obedience to rules and systems caused by internal corruption, external accumulation and environment.
The US military already has this trend. The US military not only has a close relationship with the arms industry and lobbyists, but also has experienced serious internal corruption. The military court's lenient punishment for war crimes, corruption and sexual assault by American soldiers also shows that the institution does not always function as institutionalism and military nationalization promise.
After all, if the agency can magically solve all problems, Liberia and the Philippines, which replicate the political system of the United States, should have become developed countries, rather than still struggling with poverty or civil war.
In the case of such capitalization of the army, structurally speaking, in the long run, the loyalty and discipline of soldiers are questionable. In order to prepare for the future, I suggest American scholars and politicians immediately study the history of the middle and late Tang Dynasty and the Five Dynasties and Ten Kingdoms period.