"For every action, there is an equal and opposite reaction" is Newton's third law of physics.
Its counterpart in geopolitics is "blowback," when military action in one sphere produces an unintended and undesirable consequence in another.
September 11, 2001, was blowback.
George H.W. Bush had sent an army of half a million to hurl Saddam Hussein out of Kuwait, a triumph. He proceeded to impose severe sanctions on the Iraqis and to build U.S. bases in Saudi Arabia.
"Infidel" soldiers on sacred Islamic soil and the suffering of the Iraqi people under American sanctions were two of the causes Osama bin Laden listed in his declaration of war on the United States.
Our 3,000 dead on 9/11 were blowback for having established a neo-imperial presence in the Arabian Peninsula after Desert Storm.
In the African nation of Mali today, where al-Qaida and allies have seized the northern half of the country, Azawad, as large as Texas, we are witnessing blowback for President Obama's intervention in Libya.
How so? Due almost entirely to U.S.-backed NATO bombing, which prevented Moammar Gadhafi from crushing the uprising of 2011, the colonel was overthrown and murdered by rebels.
Tauregs from Mali, whom Gadhafi had brought into his army, fled or were expelled from Libya. Taking their heavy weapons, they returned to a country where their people had been mistreated and seized its northern half, to secede and create their own nation.
But the jihadists who fought alongside them to capture the north turned on them and drove them from power. Ansar Dine and al-Qaida in the Islamic Maghreb -- like the Taliban in Afghanistan who blew up the ancient Bamiyan Buddhas -- then blew up all non-Islamic shrines and imposed a brutal form of Sharia law.
Adulterers are subject to stonings. Thieves have their hands amputated.
This is but part of the strategic disaster, however. The U.S.-trained Malian army collapsed in the face of the rebellion. U.S.-trained Malian troops defected to the jihadists. A Malian captain trained at Ft. Benning overthrew the democratic government in Bamako and seized power.
This situation had festered for 10 months. Then, this month, the jihadists occupied Konna and threatened Mopti, south of the dividing line, and Islamists entering Mali from Mauritania seized Diabaly, only 250 miles from Bamako. The whole of Mali seemed about to fall to al-Qaida.
France, whose colony Mali was, reacted. Prime Minister Francois Hollande sent planes to bomb the Islamists and 2,500 French soldiers to recapture Diabaly. That battle is now underway.
The 16-nation Economic Community of West African States has talked of raising an army to recapture the north. Thus far it has been just that, talk. While the United States has provided logistical and intelligence support to the French, Defense Secretary Leon Panetta says there will be no U.S. boots on the ground.
French troops and air power can probably clear and hold the south, but who is going to march north to drive AQIM and its allies out?
Twenty-five hundred French soldiers could not both invade and hold Azawad. Even should they recapture northern towns like Timbuktu, they could not hold the region against a determined guerrilla war that al-Qaida and its allies could mount.
Yet Hollande says he will restore the territorial integrity of Mali.
French bombing is already causing civilian casualties. This could produce blowback in France, where thousands of Malians have emigrated. Many French yet remember the homeland terrorism as they fought their eight-year war from 1954 to 1962 to hold Algeria.
This week's seizure of Western hostages in Algeria is Islamist retaliation for Algeria's having allowed France to use its airspace in the attacks in Mali. And as Syria's civil war has brought jihadis on the run, an Islamist war against France in the Sahel region of Africa could do the same.
And how would Muslims of an inflamed Middle East accept another Western war against soldiers of the Prophet?
While Mali is of little geostrategic value, a huge and secure base camp for al-Qaida in northern Mali presents serious problems for the United States.
Al-Qaida in Mali is reportedly in contact with the terrorists of Boko Haram, who have been murdering Christians and burning their churches in Nigeria. And the reports that Islamists entered Mali from Mauritania suggest this cancer is metastasizing.
What should be done?
The United States cannot fight Mali's war. No vital interest is imperiled there, and this could lead to an Afghanistan in the heart of Africa. But if America is not going to take the lead in recapturing the Azawad for Mali, who is? France? ECOWAS? NATO? Algeria?
Without America, the will is not there, the weapons are not there, the troops are not there.
As we consider our options, however, let us hear no more from President Obama about al-Qaida being "on the run" and "on the path to defeat."
Patrick J. Buchanan is the author of "Suicide of a Superpower: Will America Survive to 2025?" To find out more about Patrick Buchanan and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate webpage atwww.creators.com.