Under capitalism, the army is made up of volunteers.
A draft (military conscription) is where the government uses the police power of the state to force citizens to fight in (and die in) wars that the citizens do not agree with. The proper name for such a hideous concept is slavery.
Writes philosopher Ayn Rand on those who support the draft:
“The most immoral contradiction—in the chaos of today’s anti-ideological groups—is that of the so-called “conservatives,” who posture as defenders of individual rights, particularly property rights, but uphold and advocate the draft. By what infernal evasion can they hope to justify the proposition that creatures who have no right to life, have the right to a bank account? A slightly higher—though not much higher—rung of hell should be reserved for those “liberals” who claim that man has the “right” to economic security, public housing, medical care, education, recreation, but no right to life, or: that man has the right to livelihood, but not to life.” [1]
In a capitalist country, there is no draft, in which governments can force their citizens to fight wars.
What will a capitalist country do if it is attacked? If a capitalist country is attacked it will retaliate and defend itself using the most powerful kind of army possible: a volunteer army of individuals who do not wish to live their lives as slaves.
[1] Ayn Rand “The Wreckage of the Consensus” Capitalism: The Unknown Ideal 226