The phrase "constant attack" means a continuous and persistent onslaught or barrage against something. It implies that there is an aggressive, unrelenting effort to undermine, damage or destroy whatever is being targeted. The attacks may come from different sources, but they are all directed towards the same goal - to weaken, subdue or eliminate what is under attack. In essence, it means a state of constant vulnerability and defensiveness as one tries to fend off the relentless onslaught of the enemy.