Every nation has the right to demand proper treatment and no country should violate the territory of any other country. Mustafa Kemal Atatürk

Introduction
From the early history itself it’s evident that many countries invaded other countries for many purposes which included expanding their precious empire.Great Britain is the best example for the military invasions, as it has invaded almost 90percent of the world’s countries. ”Sun never sets on the British Empire” is a famous slogan that shows the power of the Great Britain by invading the countries.Similarly many other countries also tried their hand in invasion and conquered and ruled them. Although every country has the right to not be invaded, countries like Great Britain invaded other countries to strengthen themselves and exploit the other.For these invasions they made use of their military.

An invasion is a military offensive in which large numbers of combatants of one geopolitical entity aggressively enter territory owned by another such entity, generally with the objective of either conquering; liberating or re-establishing control or authority over a territory; forcing the partition of a country; altering the established government or gaining concessions from said government; or a combination thereof. An invasion can be the cause of a war, be a part of a larger strategy to end a war, or it can constitute an entire war in itself. Due to the large scale of the operations associated with invasions, they are usually strategic in planning and execution.

History
History of military invasions dates back decades and even centuries.For example, German military operations conducted against Poland in 1939 which precipitated World War II are often called the Invasion of Poland, while military operations conducted against Nazi-controlled France in 1944 for the purpose of liberation are called the Invasion of Normandy.[1] Archaeological evidence indicates that invasions have been frequent occurrences since prehistory.

In antiquity, before radio communications and fast transportation, the only way for a military to ensure adequate reinforcements was to move armies as one massive force. This, by its very nature, led to the strategy of invasion. With invasion came cultural exchanges in government, religion, philosophy, and technology that shaped the development of much of the ancient world.

Methods of military invasion

1. Invasion by land:
   Invasion over land is the straightforward entry of armed forces into another country, using existing land connections, usually crossing borders or otherwise defined zones, such as a demilitarized zone, overwhelming defensive emplacements and structures. Although this tactic often results in a quick victory, troop movements are relatively slow and subject to disruption by terrain and weather. Furthermore, it is hard to conceal plans for this method of invasion, as most geopolitical entities take defensive positions in areas that are most vulnerable to the methods mentioned above.
    
2. Invasion by Sea:
   Invasion by sea is the use of a body of water to facilitate the entry of armed forces into an area, through the sea, often to a landmass adjoining the body of water or an island. This is generally used either in combination with another method of invasion,such as entry through the sea further requires entry to the land by invasion by land. And especially before the invention of flight, for cases in which there is no other method to enter the territory they used this method. The merits of this method includes of the ability to perform a surprise attack from sea, or that naval defences of the area in question are inadequate to repel such an attack.
   
   But along with these merits there are difficulties that the large amount of specialized equipment, such as amphibious vehicles and the difficulty of establishing defences—usually with a resulting high casualty count.Even though there are such a risk are success rate is very low. These are often said as arguments against such an invasion method. Underwater hazards and a lack of good cover are very common problems during invasions from the sea. At the Battle of Tarawa, Marine landing craft became hung up on a coral reef and were shelled from the beach. Other landers were sunk before they could reach the shore, and the tanks they were carrying were stranded in the water. Most of the few survivors of the first wave ended up pinned down on the beach. The island was conquered but at a heavy cost, and the loss of life sparked mass protests from civilians in the United States.[2]
    
3. Invasion by Air:
   Invasion by air is an invention of the 20th century and modern warfare. The idea involves sending military units into a territory by aircraft. The aircraft either land in the other countries territory, allowing the military units to debark and attempt their objectives, or the troops climb down the aircraft while the aircraft is in the air itself, using parachutes or similar devices to land, in the territory being invaded.

This type of invasion also will follow a combination of methods of invasions, after landing from the aircraft the troop should either invade by the land or by sea. Many times, air assaults have been used to pave the way for a ground- or sea-based invasion, by taking key positions deep behind enemy lines such as bridges and crossroads, but an entirely air-based invasion has never succeeded.

Advantages of this method relate to the ability to target specific areas that may not necessarily be easily accessible by land or sea, a greater chance of surprising the enemy and overwhelming defensive structures, and, in many cases, the need for a reduced number of forces due to the element of surprise. Disadvantages typically involve the capacity to perform such an invasion—such as the number of planes that would be needed to carry a sufficient number of troops—and the need for a high level of intelligence in order for the invasion to be successful.

Defence
States with potentially hostile neighbours typically adopt defensive measures to delay or forestall an invasion ,may be by way of applying more military force in the borders or building forts etc. in addition to utilizing geographical barriers such as rivers, marshes, or rugged terrain. Such a defence can be intended to actively prevent invading forces from entering the country by means of an extended and well-defended barrier; the Great Wall of China [3], Hadrian's Wall [4], and the Danewerk [5] are famous examples.

Such barriers have also included trench lines and, in more modern times, minefields, cameras, and motion-sensitive sensors to sense the presence of the enemy. However, these barriers can require a large military force to provide the defense, as well as maintain the equipment and positions, which can impose a great economic burden on the country. Some of those same techniques can also be turned against defenders, used to keep them from escape or resupply. During Operation Starvation, Allied forces used airdrop mines to severely disrupt Japanese logistical operations within their own border [6].

Impact of the invasions
The outcomes of an invasion may vary according to the objectives of both invaders and defenders, the success of the invasion and the defence, and the presence or absence of an agreed settlement between the warring parties. The most common outcome is the loss of territory, generally accompanied by a change in government and often the loss of direct control of that government by the losing faction.

This sometimes results in the transformation of that country into a client state, often accompanied by requirements to pay reparations or tribute to the victor. In other cases the results of a successful invasion may simply be a return to the status quo; this can be seen in wars of attrition, when the destruction of personnel and supplies is the main strategic objective, or where a nation previously subdued and currently occupied by an aggressive third party is restored to control of its own affairs (i.e. Western Europe following the Normandy landings in 1944 [7], or Kuwait following the defeat of Iraq in 1991). In some cases, the invasion may be strategically limited to a geographical area, which is carved into a separate state as with the Bangladesh Liberation War in 1971.

Pacification
Pacification is an attempt to create or maintain peace. That can mean appeasing a hostile country through diplomacy or even just by settling an argument. A pacifist is someone who is against fighting and wars.Pacification is the requirement of the time that these ambitious invasions leads to many economical,geographical losses. While through the pacification the arguments which may lead to war can be controlled by this peacemaking method.

Conclusion
China is constantly in the news for its ambition to be a super-power by invading India and Taiwan.China tries to bring Taiwan to its control as it brought out the control over Hong-Kong as part of their ‘One China Policy’.Similarly many other countries also look forward to invade another country and bring them to their control and thereby become a superpower in the world which they things will definitely brings a benefit in many ways in terms of trade benefits,legislation powers etc.but in this era it is important to make a harmonious relationships with all countries.

References

1. https://www.newworldencyclopedia.org/entry/Invasion#:~:text=For%20example%2C%20German%20military%20operations,called%20the%20Invasion%20of%20Normandy
2. https://www.google.com/amp/s/www.history.com/.amp/topics/world-war-ii/battle-of-tarawa
3. https://www.history.com/topics/ancient-china/great-wall-of-china
4. https://www.google.com/amp/s/www.history.com/.amp/topics/ancient-rome/hadriansDanewirk
5. https://www.britannica.com/topic/Danewirk
6. https://www.historynet.com/operation-starvation.htm
7. https://www.britannica.com/event/Normandy-Invasion
8. https://www.google.com/amp/s/www.history.com/.amp/this-day-in-history/iraq-invades-kuwait