BANGKOK (AFP) -- Myanmar's secretive junta leader Than Shwe remains firmly entrenched as head of state of one of Asia's poorest nation's despite control of the armed forces shifting to his trusted protege.

Senior General Than Shwe has ensured his own future personal security by agreeing to his deputy taking over as commander-in-chief in the first major shift for more than a decade, according to sources.

Shwe Mann was the military's joint chief of staff and its third-most powerful man who had been personally groomed by Than Shwe for the job.

The move appeared designed to ensure that the junta's iron-fisted rule will continue as the 73-year-old supremo, who keeps his nation under a blanket of fear, begins to worry about his age and his health, analysts said.

"Shwe Man taking over as commander in chief has been long in the pipeline," said Aung Naing Oo, a Myanmar analyst based in Thailand.

"This guy has been instructed by the leadership" to prepare him for the post, he added.

As the senior general leading the junta, Than Shwe has styled himself as a reincarnated king, creating a new capital outside the central town of Pyinmana.

While Than Shwe is generally seen both inside and outside of the country as a malevolent leader catering to his personal whims and fancies, as well as that of his wife and four children, he appears to see himself as a visionary.

"Despite everything, he obviously wants to go down in history as a benevolent king," one analyst in Yangon said.

He has embarked on a vast campaign of public works in the fashion of the ancient monarchs even as the economy crumbled, building pagodas, bridges, roads, dams and irrigation canals.

But he began life more humbly. Than Shwe's first job was as a postal clerk in Meikhtilar, a thriving business town near Mandalay where the main air force base is located. At age 20, he enlisted as an officer-cadet in the army of his newly independent nation.

He rose through the ranks, working for a time in a roving psychological-warfare unit, until becoming deputy defence minister in 1985.

When pro-democracy unrest broke out in 1988, former dictator Ne Win fell from power and a military junta took control, with Than Shwe among its 21 members.

The junta organized elections in 1990, which were won -- to the military's great surprise -- by the upstart National League for Democracy, headed by Aung San Suu Kyi.

The military never allowed the NLD to take power, and after Than Shwe became the junta's leader in 1992, he officially voided the election results and detained Aung San Suu Kyi -- even as she received the Nobel Peace Prize.

Instead he launched the process of writing a new constitution, which he claimed was needed before the military could hand over power. That process is still ongoing, with a new round of talks due to start next month.

Than Shwe has kept Aung San Suu Kyi under house arrest for more than 10 years in three major periods of detention, and left her NLD marginalized.

He has been equally harsh with his rivals within the military.

In October 2004, he sacked General Khin Nyunt, the then-prime minister and powerful chief of the pervasive military intelligence organization, which had been an important and feared instrument of the junta.

Than Shwe dismantled the entire military intelligence network, detained Khin Nyunt and his family, as well as hundreds of his allies.

Khin Nyunt had been perceived as something of a moderate, who was at least willing to speak with the international community.

He had sold Than Shwe the idea of a seven-step "road map" to democracy, hoping to convince the world that reforms were coming.

But Than Shwe has opted to use the process as a stepping stone to guarantee his personal security in the future, pushing his constitutional project as a means to enshrine his power.

"What he is aiming for is his future security, personal supremacy, military supremacy and legitimacy -- all in that order," said one analyst in Myanmar, speaking on condition of anonymity for fear of retribution.