Find em, then kill em; search and destroy, until they were all gone (war of attrition).
The South.
Fight Germany first while defending critical Pacific sea routes and islands.
Defending South Vietnam against Communist aggression from North Vietnam.
The small population hindered the South's ability to defend its vast area. As it was, the Army of Northern Virginia did a good job defending Richmond, but the rest of the South lay more or less open to invasion. The South never really formulated a war policy that would allow for an elastic defense. In short, there were too few troops defending too much territory without a coordinated strategy.
The South Vietnamese
N. Vietnam was ATTACKING S. Vietnam. South Vietnam was defending itself with the help of the US/Allies.
Australia developed a defensive strategy of abandoning the North and defending the 'Brisbane Line'.
The civil war was fought by the North and the South, both parts of the U.S. Are you talking union or confederate?
Vietnamisation
Bubba Watson
In the US Civil War, the North had the advantage in population and industry. The South had the advantage of better officers, and that they were defending their homes.
The South's greatest advantage in the US Civil War was the fact that it would be defending its own territory. It was important to know the Southern terrain, to know its own liabilities, and be in a position to correct them before the Union knew the weaknesses existed.