He got underneath the elephant, stabbed it from beneath, and killed it: It is possible to combine stabbed it from beneath, and killed it as “and stabbed it to death” (Good News Bible, Contemporary English Version). But translators may also say “and killed it by stabbing it with his sword.”
But it fell to the ground upon him and there he died: Eleazar killed the elephant in order to expose the king himself to danger (thinking the king was on the elephant), but it fell on him and crushed him to death. Contemporary English Version‘s model is helpful: “But the heavy elephant sank down and crushed him.”
As noted above, it is possible to combine verses 44-46 as follows:
• Determined to reach that huge elephant, Eleazar ran right into the middle of the group of foot soldiers protecting it. As he charged in, he killed men all around him, and the enemy soldiers let him through [or, moved out of his way]. He ran underneath the elephant and stabbed it to death with his sword. But the beast fell on him and crushed him. Eleazar gave up his life to save his people, and will never be forgotten.
Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Maccabees. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here.
