Entrenched

The enemy was entrenched all around the capital.

Source: tatoeba (278694)

We had to run the gauntlet of entrenched defenders.

Source: tatoeba (2027622)

The post-war economic development of vanquished nations can be rapid if they are not looted by the victors. For this there are two reasons. First, everything has not been destroyed: some things are merely broken; and a relatively small effort of rehabilitation is multiplied by the value of what remains serviceable. Second is the disabling of entrenched power structures, which often stand as a bar to progress.

Source: tatoeba (2040450)

Yes, in America, there is too much money in politics; too much entrenched partisanship; too little participation by citizens, in part because of a patchwork of laws that makes it harder to vote.

Source: tatoeba (5774042)