From a land that is often the source of exotic or disconcerting news, the reports of recent weeks coming out of Yemen have been especially worrying. The news is bad for the stability and security of the region in which Yemen is located, for the broader regional conflict between radical, terroristic, Islamism and its opponents, and, most of all, for the 20 or more million long-suffering people of that country itself.

At a time when Yemen's oil revenues, never large (output hit, at the most, 400,000 barrels a day), have started to decline, when tourism has all but come to a halt, and when a zone of insecurity reigns in the waters of Aden and in neighbouring Somalia, mass protests have broken out in the southern part of the country.

In the port of Aden demonstrators have been killed, newspaper offices occupied by the army and closed. In the far north of the country, around Sada, a tribal insurrection, led by elements of the Al Huti family, continues. In a country where political statements are usually chloroformed in formal terminology, a tone of palpable alarm can be heard.

In what must count as a serious warning to the political leaders of the Yemen, and their opponents, the presidential adviser and former leader of FLOSY, the pro-Egyptian nationalist movement against the British in Aden, Mohammad Basendwah, has declared that the country is now in the most serious crisis he has ever seen – and he is a man who has seen a protracted war in the north in the 1960s, years of guerrilla war against the British in the south, two wars between independent Yemeni states and the inter-Yemeni civil war of 1994.

Meanwhile Sheikh Hamad Al Ahmar, son of the once powerful tribal leader Abdullah Al Ahmar, who, as I learnt when I visited him in 1992, had a house in Sanaa that included a private jail in the basement, has called on behalf of the united opposition forces for a change of policy and recognition of the seriousness of the situation.

Among his associates are the Yemeni Socialist Party, former rulers of the pro-Soviet south: Al Ahmar and others are now called for the return from exile of YSP leaders who fled the country after the north-south civil war of 1994, in which the north vanquished the south. Chief among these is Ali Al Bid, former secretary-general of the YSP, who has lived, almost incommunicado, in Muscat since that time.

The roots of this crisis lie in the flawed unification of two separate Yemeni states in May 1990, of what were formerly the Yemeni Arabic Republic in the north, and the People's Democratic Republic of Yemen, in the south. No unification is easy – as the histories of Germany, Italy and the USA remind us – but this one was exceptionally badly planned and executed.

No-one who knew Yemen in the 1970s and 1980s, as I did, could doubt the deep commitment to unity which nearly all Yemenis, ordinary people and intellectuals alike, felt. The sense of historic and cultural unity, fragmented in the early eighteenth century, was compounded by a belief that, once united, the Yemenis would be able to face up to their greatest enemies, the Saudis, and reclaim their rightful place as, with Egypt, the most ancient of Arab lands.

After two decades of rivalry between the two Yemeni regimes, with their capitals in Sanaa and Aden respectively, and two wars in which the two states tried by force to impose their own conception of ‘unity' on the other ( the north invading the south in 1972, with support from Libya and Saudi Arabia, the south invading the north in 1979), a gradual rapprochement took place in the late 1980s: the lessening of Soviet support to the south under Gorbachev, the exhaustion of the PDRY's experiment in Soviet-style socialism, and the prospect of oil revenues that would boost the economy of both, led Presidents Ali Abdullah Saleh and Ali al Bidh to commit to unity in May 1990.

The unification process was, however, flawed from the start. The decision to go for unity, and within a matter of months, was taken spontaneously by the two leaders, so, it is, said, while driving in a car through a tunnel in Aden, and without the consent of many of their advisers or any serious thought to implementation.

External factors may also have played a part: apart from receiving a green light from, respectively Riyadh and Washington (for Sanaa) and Moscow (for Aden), the two leaders were greatly encouraged by Iraq: Saddam, at that time recovering from the war with Iran which ended in August 1988, and looking to build a broad anti-Saudi and anti-Egyptian alliance provided political and, it is said, some financial support to the two leaderships.

The full import of the Iraqi support for a united, and, implicitly, anti-Saudi Yemen only became clear some months later, with the invasion of Kuwait in August 1990. This provoked a major crisis for Yemen: hundreds of thousands of Yemenis were summarily expelled by Saudi Arabia, which, as did Washington, cut off all aid to Saleh.

Yemen was also, to its misfortune, in the international limelight holding at that time a seat on the UN Security Council: represented by its long-standing representative, Abdullah Al Ashtal, it abstained in the crucial vote on armed action against Iraq, and, in so doing, incurred the wrath of the USA.

The years that followed only served further to sour the initial and genuine popular enthusiasm of May 1990. The northern elite around Saleh saw unification as an opportunity to take hold of the resources of the south – oil revenues, British colonial villas in Aden, local trade.

The negotiated merger of 1990 soon gave way to conflict and in May 1994 the President launched a war to destroy the military and political presence of the YSP in the south: in ‘The Seventy Day War', which ended with the occupation and pillage of Aden in July 1994, the northern army, with superior weapons and numbers, the benefit of surprise and, not least, the support of Islamist militia forces linked to Al Qaida, prevailed.

The story since then has been one of increased tension, and resentment, between the two former states. Some measures have been taken to disguise this process: some of the southern political and military leadership were incorporate into the northern state; periodic, but in effect meaningless, elections were held for parliament and the presidency; gestures of reconciliation and political reform were made to assuage credulous western governments and NGOs.

In the south, however, these meant little and southerners came increasingly to resent northern intrusion, referring to northerners as atrak, ‘Turks', a reference back to the Ottoman occupation of the nineteenth century, and dahbashah, the name of a criminal family in a TV series.

Regime spokesmen are these days blaming foreigners and enemies of Yemen for the crisis: however, the main responsibility for this conflict, and for the squandering of what was, in its inception, an important and positive unificatory initative, must lie with Saleh, his close associates and his relatives: ‘Abu Ahmad', as he is known, the architect of Yemeni unity, has also been the person who has done more than anyone else to destroy it.

Fred Halliday is ICREA Research Professor at the Barcelona Institute for International Affairs.