en_tn_condensed/hos/05/13.md

When Ephraim saw his sickness, and Judah saw his wound

Both Ephraim (the northern kingdom of Israel) and Judah (the southern kingdom of Israel) realized that they were in danger. (See: rc://en/ta/man/translate/figs-metaphor)

then Ephraim went to Assyria, and Judah sent messengers to the great king

Ephraim and Judah asked Assyria for help instead of asking Yahweh for help. "Great king" was a title for the king of Assyria.

But he was not able

Here "he" refers to the king of Assyria.