Simple answer he didn't kill that many people. I don't know what the real number casualties are but it certaintly wasn't 50 -200k or whatever exaggerated wikipedia estimates they make up.
There was no Isaaq genocide. Those numbers are not independently verified and most would have probably died of famine and starvation due to the deteriorating situation in the North which not only affected the city but the general country side which was insecure. Others died in the decades/years after from the infighting after the governments collapse.
It was one insurgent group SNM attacking the north blowing things up, doing several combined attack with the Ethiopian army, massacring people in their homes and doing general terrorist acts and it was the Somali national army defending against it. The government was 100% in a defense posture throughout it and launching counter offensives , they were reacting to unprovoked attacks.
SNM was founded in Ethiopia and was using Ethiopia as a base to launch attacks from while the people in the in northern Somalia suffered from a counter offensive, , destroying refugee camps, somali towns in Ethiopia, highjacking planes/ships and preventing humanitarian aid, kidnapped refugee workers, hostage taking , assassinating officials and innocent people, causing people to flee.
The SNM even launched combined attack with Ethiopian Army on Borama , killing a bunch of school children, and caused 80.000 people to flee .They blowed up hospitals and building in Hargeisa.
They would do hit and run, while innocent people suffered from a counter offensive. SNM would wear plain clothing and hide amongst the civilian population, in order to bring the civilian population into it and provoke the Somali government.
They jumped on roof tops of various houses and buildings , with machines guns and rocket launchers shooting at people, before the government resorted to Arial assaults targeting them from above.
We have various eye witness accounts, monitoring groups and local testimonies from the populations living there to support this.
The supplies to the north was cut off by the southern insurgent groups and not by the government that was battling the government because the same national army in the north was dying from starvation as well towards last year or two.
If we ignore the unverifiable numbers, which make no sense and evaluate the governments response, there is several things that prove that this was not a genocide.
1) Siad Barre is recorded to order restraint and leniency from his soldiers on the civilian populations
2) From the time of the first insurgency attack until they invaded in the two cities 1988 , the government avoided hitting population centers, gave clear warnings for people to flee and
3) The government payed compensation fees to families affected by the conflict
4) Allowed humanitarian aid & international workers into the area, UN inspectors , to provide relief.
5) The government built camps to house people in safe areas away from conflict.
6) He even tried to create avenues for peace treaties with SNM, reconcilation and open dialogue with them, constantly negotiating with them to end the fight. But they refused it. And even encouraged the US to lead effors of reconciliation and rehabilitation as a neutral third party. He even appointed various northern and other local leaders into a constitutional committee to achieve national reconciliation.
7) Siad Barre commisioned the two cities infrastructure to be rebuilt, hospitals and humanitarian facilitiaties and programmes etc. The united states donated 1 million and provided assistance distrubituted through the Somali government.
So in short there was not attempt made by the government to bring about the destruction of Isaaq or the north in general. It's just an easily disprovable lie . SNM sought to draw out the government to use civilians deaths as propaganda.
They also invent this mythology that they were able to defeat the government when they actually was defeated and repulsed each time and was only able to enter the cities a few moments after the central government collapse. After that they went on a hunting spree targeting innocent Somalis , infighting amongst their ranks and collectively punishing Somalis with unionist asperations. They had zero policy, vision or unitary governmental plan.