What was Nixon's plan to "win" the Vietnam War? How did this plan involve Cambodia?

President Nixon had a three parts to his plan to end the war.

First, he wanted the North Vietnamese to withdraw their military from the South.

Second, he wanted to end the kind of domestic unrest that was causing the protests against the war at home.  He did this by making the draft fairer and eventually ending it.

Third, he wanted to fight the war more aggressively.  This included bombing Cambodia because there were places in that country where communist troops would set up bases in safety (because the US would not attack them in a neutral country.)