Etymology and English translation based on Anvaya (logical connection of words) of Maharshi Dayanad Saraswati (M.D.S)- -

He=O! (saṃtya)= who has full knowledge to give good conduct, (īśvara)=God, (yathā)=like, (haviṣmantaḥ)= Able to give and take things like ghee, food etc. (janāsaḥ)= scholars who became famous in knowkdge, (yasya)=whose, (te)=your, (āśrayam)=shelter, (dadhire)=take shelter, (tathā)=in the same way, (tam)=to that, (sahovṛdham)= boosting force, (agnim)=God who protects all, (tvām)=you, (vayam)=we, (vidhema)=must attend, (saḥ)=god, (sumanāḥ)= whose inner knowledge is graceful, such, (tvam)= forever happy, (adya)=on to day itself, (naḥ)=to us, (iha)=in this world, (ca)=and, (vājeṣu)=in wars, (avitā)= The one who enters into all the disciplines known as the protector, (bhava)=be.

English Translation (K.K.V.) -

O God! Who has perfect knowledge to give to the one having good conduct. Like the learned people who are famous for the knowledge of giving and taking things like ghee, food etc., whose you take shelter, in the same way, God who increases that strength and protects everyone, may we attend Him. May God, whose mind is full of glory, who is always happy, on this very day, be the one to enter into all the disciplines known to us as a protector in this world and in the wars.

TranslaTranslation of gist of the mantra by Maharshi Dayanandtion of gist of the mantra by Maharshi Dayanand -

Human beings should be satisfied with the worship of a unique God, because the learned people never accept other things in the place of God with the spirit of worship, that is why they never see war or defeat in this world because they are righteous and that's why, those who do not worship God are not able to win them. Because, how can they be defeated by those, whom God is supposed to protect.