Army of the Republic of Vietnam (South) came into being on October 26, 1956, having been reorganized by the Government of President Ngo Dinh Diem. Despite much aid from various countries - the biggest being the good old USA - ARVN forces got a right good kicking from the North Vietnamese Army & Viet Cong (NVA & VC).
Or so it might seem from a simplistic reading of headlines. The truth is rather more complex. US instructors made their biggest mistake in thinking that Vietnamese military thinking was the same as their own. Not so. South Vietnamese soldiers were primarily villagers, whose peasant loyalties to their villages took precedence over any national loyalty.
Many ARVN soldiers continued to serve loyally and fight bravely, despite having family in the Viet Cong. Many other South Vietnamese soldiers led double lives, moonlighting as VC to ensure their survival should the North be victorious. Both positions are equally understandable.
After US withdrawal of combat forces on 29 March 1973, the NVA increased the pressure on the now-vulnerable South. However, it was not until December 1974 that the NVA infiltrated Phuoc Long province, with the intention of taking over the Central Highlands. General Van Tien Dung's forces took over 3 weeks to capture the provincial capital of Phuoc Binh. On 7 January 1975, the defenders surrendered, representing the first hurdle to be cleared by the North Vietnamese political leadership: the US had not intervened with B52 bombers, as they had hinted they might do.
By 10 March, the NVA had built up their invasion strength to about 3 divisions, centred on Ban Me Thout. This town had taken over 30 hours to capture, despite overwhelming force on the side of the NVA. The North Vietnamese were now in a position to drive to the Central Coast, then turn south to Saigon. Garrisons fell in quick succession: Da Nang, Qui Nhon, Tuy Hon, Nha Trang, and finally the grand prize of Cam Ranh Bay. This former US naval base would later be used by the Soviets for Indian Ocean patrols.
Finally, an estimated 6 ARVN divisions faced a total of 18 NVA divisions, across a defensive line before Saigon with the hamlet of Xuan Loc at its centre. On 9 April, 5000 troops of Brigadier-General Le Minh Dao's 18 Div repulsed 40000 NVA. The North finally took the town on 21 April. On the same day, President Thieu resigned. His eventual successor, General Duong Van Minh, retreated to the Presidential Palace in Saigon to await the inevitable.
On 29 April, NVA artillery and air strikes closed Tan Son Nhut airport - the end was not far away. The following day, a North Vietnamese T55 tank gave its driver the biggest headache of the war: It crashed through the gates of the Presidential Palace in a symbolic end to the war. All things considered, the ARVN exceeded expectations - especially after its American support was removed.