By Shirazuddin Siddiqi
Afghan President Hamid Karzai is facing the loss of one his most respected colleagues, interior minister Ali Ahmad Jalali.
Mr Jalali is not the first Afghan minister to "return to academia"
On Tuesday Mr Jalali said he was resigning, amid reports of disagreements with the president over the appointment of warlords to provincial posts.
On the record, Mr Jalali was giving little away.
"Maybe there are reasons for [my resignation] and maybe not, but one of the main reasons is that I wish to resume my academic research," he told a private TV station in Kabul. "I feel really comfortable in that field."
But a senior government official who wish to remain unnamed told the BBC that Mr Jalali was resigning because he wanted to be tough on drug dealers, specially those within the government, but this had not proven to be possible.
Mr Jalali's departure will significantly weaken the voice against drugs, corruption and warlords in the cabinet.
Mr Jalali's three years in office earned him a reputation as the key anti-drugs, anti-warlords and anti-corruption minister in the Afghan government.
These issues concern both Afghans and the international community which has been supporting the Afghan government since late 2001.
Mr Jalali, in his early 60s, has publicly accused senior government officials of involvement in the drugs trade.
Mr Jalali threatened to publish a list of officials involved in drugs trading
He also said the government was in possession of a list of those involved in drugs trading and threatened to publish the list.
Analysts say the first rift between Mr Jalali and President Karzai emerged when the president, under pressure from hardliners after his election in October 2004, decided to apply a constitutional requirement which barred people with dual nationality from holding ministerial position.
Mr Jalali, who also holds an American passport, was said to be so disappointed at the decision that he left the country before the cabinet was announced.
In the end a compromise was reached, and Mr Jalali returned.
Mr Jalali is not the first Afghan minister to "return to academia".
The president excluded Ashraf Ghani Ahmadzai - who was the government's key strategist - from his cabinet in 2004.
Mr Ahmadzai went off to head Kabul university after losing his post of finance minister.
This was seen as a major blow to US-led efforts to encourage the formation of a modern technocratic government in Afghanistan.
President Karzai's decisions over his 2004 cabinet were driven by several factors. One was the need to appease the various Islamic factions - a consideration that did not help Mr Karzai form a strong cabinet.
It has very few members who can effectively work with the international community to foster their cooperation in the reconstruction of the country.
Officials and analysts have also said that Mr Jalali has been at odds with Mr Karzai over the president's appointments to important provincial posts because of concerns that they would pursue factional interests, rather than national ones.
Several provincial positions are held by warlords who are not necessarily prepared to take orders the central government.
Mr Jalali's resignation move follows parliamentary and provincial councils elections held on 18 September.
Some had expected him to wait for the formation of the parliament before announcing his decision.
It is too early to say what the wider implications of Mr Jalali's departure will be for President Karzai.
Some critics say the resignation reflects badly on Mr Karzai's managerial abilities. They feel he is not particularly good at handling strong personalities.
So who will replace Mr Jalali? That is a key question on the mind of Afghans and their international supporters.
Whether Mr Karzai picks up somebody from one of the factions, or a moderate technocrat who can help strengthen the relations with international community, he will have to think hard before making a final decision.