Complex sentence: Many Polish people believe Edward Rydz-Śmigły to be the poem's author; however, it is unlikely that Rydz, a Polish military leader, would have written a poem in Czech.
Split into simpler sentences: Many Polish people believe Edward Rydz-Śmigły to be the poem's author. However it is unlikely that Rydz, a Polish military leader, would have written a poem in Czech.