A dramatic rise in the number of aerial sorties over the sea separating the Chinese mainland from Taiwan has served as a reminder that the strait has the potential to be one of the most dangerous places on Earth. A reported 149 incursions in four days by People’s Liberation Army planes into Taiwan's air defence zone have left the de-facto independent island on high alert as it warned that China could be capable of invading by 2025. As global leaders keep a close eye on the worsening relations in the region, Guardian correspondent Helen Davidson explains why and how tensions could escalate into war

• Taiwan and China: line that Biden must tread is finer than ever

Taiwan will keep bolstering its defences to ensure nobody can force the island to accept the path China has laid down that offers neither freedom nor democracy, President Tsai Ing-wen said on Sunday, in a strong riposte to Beijing. Claimed by China as its own territory, Taiwan has come under growing military and political pressure to accept Beijing's rule, including repeated Chinese air force missions in Taiwan's air defence identification zone, prompting international concern 

• Taiwan national day: we won’t bow to China, says president amid tensions