In his classic work, Apologetics to the Glory of God: An Introduction, John Frame distinguishes 3 aspects of apologetics:

1) Apologetics as proof: Jesus and His apostles offered evidence to those having difficulty believing the Gospel as true (note  John 14:11; 20:24-31; I Cor. 15:1-11)

2) Apologetics as defense: Answering objections of unbelief (note Phil. 1:7; cf. v. 16)

3) Apologetics as offense: Attacking the foolishness (Ps. 14:1; I Cor. 1:18-2:16)

How does this relate to the Great Commission? Simply put, if we are unable to give an answer to the hope that is within us, we cannot be obedient in carrying out the Great Commission given by our Lord, much less obey His explicit command to disciple every nation or ethnic group.

…but in your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect, having a good conscience, so that, when you are slandered, those who revile your good behavior in Christ may be put to shame. – I Peter 3:15, 16 (ESV)