What is the main theme of the above passage?

Read the following passage and answer the questions given after it. At a number of places in the Kashmir Valley, security forces have put coils of razor wire on roads to enforce restrictions on movement. Concertina wire or razor wire fences are used along territorial borders and in areas of conflict around the world, to keep out combatants, terrorists, or refugees. The expandable spools of barbed or razor wire get their name from concertina, a hand-held musical instrument similar to the accordion, with bellows that expand and contract. Concertina wire coils were an improvisation on the barbed wire obstacles used during World War
I. The flat, collapsible coils with intermittent barbs or blades were designed to be carried along by infantry, and deployed on battlefields to prevent or slow down enemy movement. The Englishman Richard Newton is credited with creating the first barbed wire around 1845; the first patent for “a double wire clipped with diamond shaped barbs” was given to Louis François Janin of France. In the United States, the first patent was registered by Lucien B Smith on June 25, 1867, for a prairie fence made of fireproof iron wire. Michael Kelly twisted razor wires together to form a cable of wires. The American businessman Joseph F Glidden is considered to be the father of the modern barbed wire. He designed the wire with two intertwined strands held by sharp prongs at regular intervals. Barbed wire was initially an agrarian fencing invention intended to confine cattle and sheep, which unlike lumber, was largely resistant to fire and bad weather. An advertorial published in the US in 1885 under the title ‘Why Barb Fencing Is Better Than Any Other’, argued that “it does not decay; boys cannot crawl through or over it; nor dogs; nor cats; nor any other animal; it watches with Argus eyes the inside and outside, up, down and lengthwise; it prevents the ‘ins’ from being ‘outs’, and the ‘outs’ from being ‘ins’, watches at day-break, at noontide, at sunset and all night long…” Barbed wire was put to military use in the Siege of Santiago in 1898 during the SpanishAmerican War, and by the British in the Second Boer War of 1899-1902 to confine the families of the Afrikaans-speaking Boer fighters. World War I saw extensive use of barbed wire — and German military engineers are credited with improvising the earliest concertina coils on the battlefield. They spun the barbed wire into circles and simply spread it on the battlefield. Without using any support infrastructure like poles etc. this was more effective against the infantry charge by Allied soldiers. The fence erected by India along the Line of Control to keep out terrorist infiltrators consists of rows of concertina wire coils held by iron angles. They are now commonly seen and are used to secure private properties as well.