this is situation is not so easy to tackle as it seems.

a little bit background of MQM:
After post partition, Sindhis used to have very prejudiced attitude for Muhajirs. in that reaction there were communal riots. In addition to that, Sindhis origin PPPP nominated as top leading party after the fall of Dhakka. For marginalizing PPPP, Establishment supported APMSO(All Pakistan Muhajjir student organization) and created Muhajjir Quomi Movement for two main reasons.
1. to decrease the strength of PPPP.
2. to use muhajjirs as tool to overcome on Sindhi.
Establishment provided arms and ammunition to control over Karachi. later on due to their big internal clash for power, this Muhajjir Quomi movement bifurcated into Mutahida Quomi Movement(Altaf bhai Group MQM) and Haqiqi(Afaq bhai group). Both groups were enemy of each other.
MQM stepped in politics and created two main categories:
1. white collar politicians
2. underworld mafia.
both were totally intermingled.
MQM casted their votes on gun point and being elected in Parliament that fully supported their underworld branch.
Besides land mafia, dirty politics, money mafia, and many other abuses, MQM used to kill their own Muhajjirs that belong to Haqiqi group. In that response, haqiqi targeted MQM members. They even shot Mr.Altaf Hussain but luckily he was saved and escaped to London.

Current Scenario:
in Karachi there are number of leading parties. MQM, ANP, PPPP, Jeay Sindh are on the top list. these all parties are completely concerned with illegal works. Each party has white collar leaders and huge underworld battalion. Being continuous participant of Parliament, MQM cannot tolerate anyone else in Karachi, especially ANP beacause vote of ANP is increasing day by day. About 6 million people are living in Karachi that are concerned with ANP. As the MQM has bird's eye view, they feel that if such population continues, MQM will not be the one leading party of Karachi anymore, and its power will be diminished.
For that reason, MQM has started target killing and other problems and in response ANP shows its reacton. However other parties are not far from target killing. Their hands are also in blood for their benefits.

Commence of Army in Karachi:
If army take control over Karachi, it will be great set back to present government means PPPP. PPPP always calls for democracy and army control will be totally against of rule.(Remember, Army in KPK was not solely due to PPPP but there was international pressure). In the case of Karachi, scenario is different.
MQM never wants the commence of army in karachi. If this happens MQM will surely parted from government, however if PPPP do not pressurize MQM, ANP will be exaggerated. Without MQM or ANP, PPPP cannot sustain in Parliament.
Once PPPP comes out of parliament, it will not recover its position, because sudden collapse of government, PPPP will be surely divided in sub groups.

Solution:
All the chairpersons of representing parties of Karachi should have meeting and solve this problem because this problem cannot be solved with help of meeting of their puppets. These all parties have only two solution. Either they should unite and give decisive conclusion or Army should take control.

Otherwise if this scenario continues, Karachi will be doomed in the darkness.

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Born with personality is an accident but dying as a personality is an achievement.