Just saw this post on your profile comrade. Ill briefly explain.

So Afghanistan had been an islamic monarchy for centuries, until the 1920s under a british protectorate. Entering the 1970s, it was an extremely poor completely agrarian feudal society, with illiteracy being endemic, and very few industry existing, concentrating in Kabul. Afghanistan won independence from the british through 3 wars in the late 1800s and early 1900s. This meant that their monarchy wasnt a UK puppet like in other countries such as Jordan or Iraq. This allowed them to remain neutral in the Cold War, having relations with both USA and USSR. This changed in 1973, when Muhammad Daud Khan, the Kings cousin, staged a military coup while the King was on vacation in Italy. The King abdicated and Afghanistan became a Republic, ending centuries of monarchy. Khan became dictator of Afghanistan.

Now this coup was possible thanks to the Peoples Democratic Party of Afghanistan (PDPA) aiding Khan militarily through loyal units in the military. The PDPA, founded in 1965, was a marxist leninist party. It had 2 main factions, the Parcham, who were mainly urban workers and intellectuals focused on legal party activities, and the Khalq, who were mainly countryside peasants focused on illegal activities and armed struggle. The Parcham had organized the 1973 coup. After the coup, Khan established a one party dictatorship based on progressive secularist principles, and invited several Parchamists into the government.

Make no mistake tho, Khan was an opportunist, he knew communism and leftism was becoming very popular in Afghanistan, and he wanted to coopt it under his rule, so as to stay in power and profit from it. In line with this, he sought closer ties with the USSR, to stabilize his power. Khan became an important soviet ally in the region. However, his internal policies were useless to say the least. He didnt industrialize nor do land reform. He did centralize his power even more tho, eventually leading to the expulsion of the parchamists from the government and repression of the PDPA. Due to this, the Khalq started preparing a coup against Khan to seize state power and establish socialism, which they did in 1978, in the Saur Revolution.

In this revolution, the khalq staged an uprising in Kabul and seized power. The Parcham, who were unaware of this plan, nevertheless supported it. Khan was captured and executed, and Nur Muhammad Taraki, General Secretary of the PDPA and a khalqist, became leader of the new Democratic Republic of Afghanistan (DRA), a socialist republic. Despite what western media claims, this revolution was 100% organic, it had received 0 support from the USSR and the soviets had no idea this was coming. This makes sense since Khan was a soviet ally.

Once in power, Taraki signed a Treaty of Friendship and Cooperation with the USSR and launched ambitious reforms. Education programs were launched to teach peasants how to read and write and wipe out illiteracy. Women were given full equality by law, and had the right to not wear the burka, they couldnt be forced to by their dad or husband. Land reform was launched to crush landlords and collectivize agriculture. Soviet engineers were invited to build infrastructure and industrialize the country. But ofc, not everyone liked this. Landlords and other reactionaries, were angry at the new government. And the USA knew this, they wanted to crush afghan socialism and create trouble with the USSR. Remember that Afghanistan bordered the USSR, a war in Afghanistan could very easily destabilize the USSR.

So already in 1978, way before any USSR troops entered Afghanistan, the CIA, through Pakistan, started funneling money and weapons to these reactionary groups, the mujahideen, who declared jihad (holy war) against the PDPA government. They used terrorist tactics, such as beheading soviet engineers and their families or assaulting schools, killing the teachers and kidnapping the girls to then force them into prostitution rings. Bombings in public places were also common. This was a US sponsored terrorist campaign, and was overwhelming the government who asked USSR for help already in 1978. Contrary to western lies, the USSR refused to send troops for more than a year.

As the crisis was unfolding, Hafizullah Amin, Tarakis deputy and a khalqist, believed Taraki was at fault. Amin was very radical, very opposed to islam, landlords and the petite bourgeoisie, and believed Taraki was too soft, and that tough measures would fix this. So on 14 September 1979, Amin staged a military coup against Taraki. Loyal army units stormed his residence and assassinated him. The Politburo of the PDPA then elected Amin as General Secretary.

This coup destabilized the DRA even more, and gave a very bad image of their government to afghans. It also pissed off the soviets a lot, since Taraki was their man in Afghanistan and Amin had done all of this without telling the soviets, behind their back. This also aggravated the situation. Amin, staying true to his principles, launched purges and intensified the repression against landlords, petty bourgeois and religion. This strenghtened the mujahideen cause, by making the religious peasant population feel attacked. The mujahideen started taking control of the countryside, so Amin again requested soviet military assistance on 17 December 1979.

The soviets accepted his request and started sending in troops on 25 December. However, the soviets distrusted Amin and thought he was a loose cannon. They decided to replace him with the more moderate parchamist Babrak Karmal to try to stabilize the situation. So on 27 December 1979, soviet special forces stormed Amins residence and assassinated him. The Politburo of the PDPA elected Babrak Karmal as General Secretary. From then on, the war began in full, with the USSR directly fighting the mujahideen.

So as you can see, this war was not an invasion, western media lied. Afghanistan requested the soviet military multiple times. All DRA leaders, Taraki, Amin and Karmal requested it. I hope you found this post useful. This is the context regarding the beginning of the war. Let me know if you have any questions.