Hmmm, maybe it is more than just "belief": Thou believest that there is one God; thou doest well: the devils also believe, and tremble. (James 2:19)
Jesus said Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. (Matthew 7:21), and No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day. (John 6:44), and He that hath my commandments, and keepeth them, he it is that loveth me: and he that loveth me shall be loved of my Father, and I will love him, and will manifest myself to him. (John 14:21)
Salvation is a bit more than simple "belief".
The requirements for salvation have varied from time to time, especially at the beginning. Many will not have time to find a church and be baptized and I believed they will be saved. Also I believe that perhaps others may be saved but I wouldn't personally want to bank on it.
AMEN!! [Titus 3:4-7] But when the kindness and generous love of God our savior appeared, not because of any righteous deeds we had done but because of his mercy, he saved us through the bath of rebirth and renewal by the holy Spirit, whom he richly poured out on us through Jesus Christ our savior, so that we might be justified by his grace and become heirs in hope of eternal life.
And again...
[2 Tim 1:9] He saved us and called us to a holy life, not according to our works but according to his own design and the grace bestowed on us in Christ Jesus before time began,
and yet again...
[2 Cor 9:8] Moreover, God is able to make every grace abundant for you, so that in all things, always having all you need, you may have an abundance for every good work.