In the fall of 1952 the French army encountered its most serious crisis since the disasters near the Chinese border (Chiến dịch biên giới – Borderland Campaign) at Cao Bằng, Đông Khê and RC 4 occurred in 1949 and 1950.

[3] By the late spring of 1951 General de Lattre had constructed a strong chain of defensive positions stretching from Halong Bay to Vĩnh Yên in the west and to That Diem and the sea in the south.

This de Lattre Line was designed to protect the Red River Delta and the cities of Hanoi and Haiphong from "the initial shocks of a [potential] Chinese invasion" and to serve as "mooring points for offensive operations.

Yet the groups were mobile only in the sense that they were motorized or mechanized, for their tanks, trucks, half-tracks, and armored cars were of little use in the mountainous jungles that covered much of northern Vietnam.

[5] In November 1951, General de Lattre launched an offensive operation (Tulipe) against the Việt Minh in Hòa Bình to reclaim an area he saw as vital for France's future in Indochina.

Meanwhile, the Battle raged on and General Salan, who saw the province, conversely, as an area that was hard to support and to defend, decided to withdraw his troops (Operation Amarante).

[7] In the fall of 1952 General Giap planned an offensive into the T'ai country to try and win a psychological and political victory by defeating the French garrisons in the Phan Xi Păng Mountain Range east of the Black River.

However, bad weather prevented the use of paratroopers, and the Việt Minh attackers cut off the retreat of the French forces falling back on Nghĩa Lộ.

[10] Then battle continued into Tu Le and Gia-Hoi as the 6th Colonial Parachute Battalion, commanded by Major Marcel Bigeard, fought a rear guard action.

Advancing northwest, the French quickly seized the towns of Phu Doan and Phú Yên Binh, important Việt Minh supply centers where they found large stocks of weapons and ammunition.

[13] The French could not inflict a decisive defeat on the enemy, despite a 2.5 to 1 manpower superiority in infantry and an overwhelming edge in artillery, tanks, and air support.

Only a few weeks later another major engagement developed west of the Black River line at Nà Sản, a strong point held by nine full-strength French battalions, supported by aircraft and five batteries of 105-mm.

[16] Meanwhile, to the south at Van Yen the 316th occupied that village and continued to Ba Lai which the French had been using to block Việt Minh access to the black River delta.