It depicts the bloody carnage in the fighting for the monastry Santa Engracia in Saragossa of February 8, 1809. Lejeune took part in the fighting himself and should be probably the wounded soldier near the center.
The fighting in Saragossa is considered one of the most brutal battles of the Napoleonic Wars. It is known for its extreme brutality and ferocity of the street fighting.Lejeune depicts in this detail fanatical monks and women who are heroical resisting the charging french troops.
So far, so good. Lejeune as an witness and an experienced painter gives a detailed depiction of that battle (The painting is from 1848). But all is arranged far beyond any realism. At first there are the two well arranged groups, which are confronted in an diagonal line. Then there is the spectacular (divine) light from above, which is illuminating like a spotlight the Pietà in the center.
And that's the Symbolism, in the face of the lamenting Mother with her dead son, men are slaughtering each other without any mercy!
Thats a great message and a great painting but it's not realistic. The Pietà is an pure invention of Lejeune as can be seen on the older engraving.
But that wasn't enough. Leujeune replaced even the gothic roof decorations by statues of vultures. I like especially that detail! But thats why I call it Realistic Symbolism.